Patent Publication Number: US-2019179497-A1

Title: Grouping of Cards by Time Periods and Content Types

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/975,668, filed on Dec. 18, 2015, which is a continuation of U.S. patent application Ser. No. 13/861,217, filed on Apr. 11, 2013, which claims priority to U.S. Provisional App. No.61/710,543, filed on Oct. 5, 2012, all of which are fully incorporated by reference herein in their entirety and for all purposes. 
    
    
     BACKGROUND 
     Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section. 
     Computing systems such as personal computers, laptop computers, tablet computers, cellular phones, and countless types of Internet-capable devices are prevalent in numerous aspects of modern life. Over time, the manner in which these devices are providing information to users is becoming more intelligent, more efficient, more intuitive, and/or less obtrusive. 
     The trend toward miniaturization of computing hardware, peripherals, as well as of sensors, detectors, and image and audio processors, among other technologies, has helped open up a field sometimes referred to as “wearable computing.” In the area of image and visual processing and production, in particular, it has become possible to consider wearable displays that place a very small image display element close enough to a wearer&#39;s (or user&#39;s) eye(s) such that the displayed image fills or nearly fills the field of view, and appears as a normal sized image, such as might be displayed on a traditional image display device. The relevant technology may be referred to as “near-eye displays.” 
     Wearable computing devices with near-eye displays may also be referred to as “head-mountable displays” (HMDs), “head-mounted displays,” “head-mounted devices,” or “head-mountable devices.” A head-mountable display places a graphic display or displays close to one or both eyes of a wearer. To generate the images on a display, a computer processing system may be used. Such displays may occupy a wearer&#39;s entire field of view, or only occupy part of wearer&#39;s field of view. Further, head-mounted displays may vary in size, taking a smaller form such as a glasses-style display or a larger form such as a helmet, for example. 
     SUMMARY 
     An example a computing device with a graphic display may include a timeline feature that allows a user to navigate through a sequence of ordered screens or “cards” shown on the graphic display. The cards may be ordered based on times when each card was created on the timeline of cards. For example, cards may be chronologically ordered based on the times each card was added to the timeline and displayed side-by-side on the graphic display from left to right. In some instances, an example head-mountable display (HMD) with the timeline feature may allow a wearer to focus on a single card at any given time, possibly similar to a slide show. Further, the wearer may scroll or browse through the timeline of cards to search for a specific card. As cards are continuously added to the timeline, numerous cards may accumulate over a period of time. Accordingly, the HMD may be configured to group cards on the timeline. In some embodiments, the cards may be grouped into time-based groups, possibly representing multiple periods of time. In some instances, the cards may also be grouped by content or by content type. Further, the cards may be grouped by multiple time periods and by content types within each respective time period. Yet further, the cards may be grouped based on durations between the present/on-going time period and each respective time period. As such, various embodiments for grouping cards on a timeline may be employed. 
     In one aspect, a computer-implemented method may involve (a) generating, by a computing device, one or more time-stamped bundle cards that correspond to a group of cards from a plurality of time-stamped cards, and (b) displaying a user interface for navigation of a chronologically sorted timeline of cards that spans at least a current time period and a first time period, where the timeline includes the one or more time-stamped bundle cards and one or more non-bundle cards from the plurality of time-stamped cards, and where a frequency of bundle cards in the first time period is greater than a frequency of bundle cards in the current time period. 
     In another aspect, a computing device may include a processor and a non-transitory computer-readable medium. The non-transitory computer-readable medium may be configured to store program instructions that are executable by the processor to cause the computing device to carry out functions including: (a) generating one or more time-stamped bundle cards that correspond to a group of cards from a plurality of time-stamped cards, and (b) displaying a user interface for navigation of a chronologically sorted timeline of cards that spans at least a current time period and a first time period, where the timeline includes the one or more time-stamped bundle cards and one or more non-bundle cards from the plurality of time-stamped cards, and where a frequency of bundle cards in the first time period is greater than a frequency of bundle cards in the current time period. 
     In yet another aspect, a non-transitory computer readable medium may include program instructions that are executable by a processor of a computing device to cause the computing device to carry out functions including: (a) generating one or more time-stamped bundle cards that correspond to a group of cards from a plurality of time-stamped cards, and (b) displaying a user interface for navigation of a chronologically sorted timeline of cards that spans at least a current time period and a first time period, where the timeline includes the one or more time-stamped bundle cards and one or more non-bundle cards from the plurality of time-stamped cards, and where a frequency of bundle cards in the first time period is greater than a frequency of bundle cards in the current time period. 
     In a further aspect, a system may include: (a) a means for generating one or more time-stamped bundle cards that correspond to a group of cards from a plurality of time-stamped cards, and (b) a means for displaying a user interface for navigation of a chronologically sorted timeline of cards that spans at least a current time period and a first time period, where the timeline includes the one or more time-stamped bundle cards and one or more non-bundle cards from the plurality of time-stamped cards, and where a frequency of bundle cards in the first time period is greater than a frequency of bundle cards in the current time period. 
     In yet a further aspect, a computer-implemented method may involve: (a) determining, by a computing device, a plurality of time-stamped cards including one or more cards in a current time period and one or more cards in a first time period, (b) determining respective bundling thresholds for the current time period and the first time period, where a frequency of time-stamped bundle cards in the first time period is greater than a frequency of time-stamped bundle cards in the current time period, (c) bundling cards of at least one group from the plurality of time-stamped cards into at least one time-stamped bundle card, and (d) displaying a chronologically sorted timeline of cards that spans at least the current time period and the first time period, where the timeline includes at least one time-stamped bundle card and at least one time-stamped non-bundle card from the plurality of time-stamped cards. 
     In another aspect, a non-transitory computer readable medium may include program instructions that are executable by a processor of a computing device to cause the computing device to carry out functions including: (a) determining a plurality of time-stamped cards including one or more cards in a current time period and one or more cards in a first time period, (b) determining respective bundling thresholds for the current time period and the first time period, where a frequency of time-stamped bundle cards in the first time period is greater than a frequency of time-stamped bundle cards in the current time period, (c) bundling cards of at least one group from the plurality of time-stamped cards into at least one time-stamped bundle card, and (d) displaying a chronologically sorted timeline of cards that spans at least the current time period and the first time period, where the timeline includes at least one time-stamped bundle card and at least one time-stamped non-bundle card from the plurality of time-stamped cards. 
     In yet a another aspect, a system may include: (a) a means for determining a plurality of time-stamped cards including one or more cards in a current time period and one or more cards in a first time period, (b) a means for determining respective bundling thresholds for the current time period and the first time period, where a frequency of time-stamped bundle cards in the first time period is greater than a frequency of time-stamped bundle cards in the current time period, (c) a means for bundling cards of at least one group from the plurality of time-stamped cards into at least one time-stamped bundle card, and (d) a means for displaying a chronologically sorted timeline of cards that spans at least the current time period and the first time period, where the timeline includes at least one time-stamped bundle card and at least one time-stamped non-bundle card from the plurality of time-stamped cards. 
     These as well as other aspects, advantages, and alternatives will become apparent to those of ordinary skill in the art by reading the following detailed description, with reference where appropriate to the accompanying drawings. Further, it should be understood that this summary and other descriptions and figures provided herein are intended to illustrative embodiments by way of example only and, as such, that numerous variations are possible. For instance, structural elements and process steps can be rearranged, combined, distributed, eliminated, or otherwise changed, while remaining within the scope of the embodiments as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates a wearable computing system according to an example embodiment. 
         FIG. 1B  illustrates an alternate view of the wearable computing device illustrated in  FIG. 1A . 
         FIG. 1C  illustrates another wearable computing system according to an example embodiment. 
         FIG. 1D  illustrates another wearable computing system according to an example embodiment. 
         FIGS. 1E to 1G  are simplified illustrations of the wearable computing system shown in  FIG. 1D , being worn by a wearer. 
         FIG. 2A  illustrates a schematic drawing of a computing device according to an example embodiment. 
         FIG. 2B  shows an example projection of an image by an example head-mountable device (HMD), according to an example embodiment. 
         FIG. 3  shows an example home card of an example user interface for a HMD, according to an example embodiment. 
         FIG. 4  shows example operations of a multi-tiered user model for a user interface for a head-mountable device (HMD), according to an example embodiment. 
         FIG. 5A  shows a scenario of example timeline interactions, according to an example embodiment. 
         FIG. 5B  shows a scenario for using a multi-timeline display, according to an example embodiment. 
         FIG. 6A  shows an example of using a two-fingered swipe on a touch-based UI of an HMD for zoomed scrolling, according to an example embodiment. 
         FIG. 6B  shows a scenario for using a clutch operation to generate a multi-card display, according to an example embodiment. 
         FIG. 6C  shows a scenario for using a clutch operation to generate a multi-timeline display, according to an example embodiment. 
         FIG. 7  shows a user-interface scenario including contextual menus, according to an example embodiment. 
         FIG. 8  shows a user-interface scenario including a people chooser, according to an example embodiment. 
         FIG. 9  shows a user-interface scenario with camera interactions, according to an example embodiment. 
         FIG. 10A  shows a user-interface scenario with photo bundles, according to an example embodiment. 
         FIG. 10B  shows a user-interface scenario with message bundles, according to an example embodiment. 
         FIG. 11A  shows a scenario with cards grouped on a timeline, according to an example embodiment. 
         FIG. 11B  shows a scenario with cards grouped by bundling cards, according to an example embodiment. 
         FIG. 11C  shows data capacity of a timeline, according to an example embodiment. 
         FIG. 11D  shows a scenario with cards grouped on a timeline and the timeline as provided by an HMD, according to an example embodiment. 
         FIG. 11E  shows a scenario of a timeline with groups of cards available on the timeline, according to an example embodiment. 
         FIG. 11F  shows a scenario of timeline data, according to an example embodiment. 
         FIG. 12A  is a flow chart illustrating a method, according to an example embodiment for grouping cards. 
         FIG. 12B  is a flow chart illustrating another method, according to an example embodiment for grouping cards. 
         FIG. 13A  shows an example visual stack, according to an example embodiment. 
         FIG. 13B  shows another example visual stack, according to an example embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Example methods and systems are described herein. It should be understood that the words “example” and “exemplary” are used herein to mean “serving as an example, instance, or illustration.” Any embodiment or feature described herein as being an “example” or “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or features. In the following detailed description, reference is made to the accompanying figures, which form a part thereof. In the figures, similar symbols typically identify similar components, unless context dictates otherwise. Other embodiments can be utilized, and other changes can be made, without departing from the spirit or scope of the subject matter presented herein. 
     The example embodiments described herein are not meant to be limiting. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are explicitly contemplated herein. 
     A. Overview 
     In an example embodiment, a UI for an HMD can include a timeline feature that allows the wearer to navigate through a sequence of ordered screens. In the context of such a timeline feature, each screen can be referred to as a “card.” Among the sequence of cards, one or more cards can be displayed, and of the displayed card(s), one card can be “focused on” for possible selection. For example, the timeline can present one card for display at a time, and the card being displayed can also be the card focused on. In one embodiment, when a card is selected, the card can be displayed using a single-card view that occupies substantially all of the viewing area of the display. 
     Each card can be associated with a certain application, object, or operation. The cards can be ordered by a time associated with the card, application, object, or operation represented by the card. For example, if a card shows a photo captured by a wearer of the HMD at 2:57 PM, the time associated with the card is the time associated with the underlying photo object of 2:57 PM. As another example, a card representing a weather application can continuously update temperature, forecast, wind, and other weather-related information. As such, the time associated with the weather application can be the present time. As an additional example, a card representing a calendar application can show an appointment in 2 hours from now, and so the time associated with the card can be a time corresponding to the displayed appointment, or 2 hours in the future. 
     The timeline feature can allow the wearer to navigate through the cards according to their associated times. For example, a wearer could move their head to the left to navigate to cards with times prior to a time associated with the focused-on card, and to the right to navigate to cards with times after the time associated with the focused-on card. As another example, the wearer can use a touch pad or similar device as part of a touch-based UI to make a swiping motion in one direction on the touch-based UI to navigate to cards with times prior to the time associated with the focused-on card, and make a swiping motion in another direction to navigate to cards with times after the time associated with the focused-on card. 
     Upon power up, the HMD can display a “home card,” also referred to as a home screen. The home card can display a clock, and be associated with a time of “now” or a present time. In some cases, the home card can display a clock, to reinforce the association between the home card and now. Then, cards associated with times before now can be viewed in the timeline as prior to the home card, and cards associated with times equal to or after now can be viewed in the timeline subsequent to the home card. 
     After viewing cards on the timeline, the wearer can choose to interact with some cards. To select a card on the timeline for interaction, the wearer can tap on the touch-based UI, also referred to as performing a “tap operation,” to select the focused-on card for interaction. In some cases, a “contextual menu” can be used to interact with the selected card. For example, if the selected focused-on card shows a photo or an image captured by the HMD, the contextual menu can provide one or more options or operations for interacting with the selected photo, such as sharing the image with one or more people, or deleting the photo. 
     Different contextual menus can be used for different objects. For example, a contextual object for a contact or representation of information about a person can have options or operations such as call the contact, send a message to the contact, delete the contact, or review/update contact details such as telephone numbers, e-mail addresses, display names, etc. 
     Lists of some objects can be arranged by a different order other than the time-based order used by the timeline. For example, a list of contacts can be arranged by frequency of contact; e.g., a contact for the person most-communicated-with using the HMD can be displayed first in a list of contacts, the second-most-communicated-with contact can be displayed second in the list, and so on. Other orderings are possible as well. 
     A group of cards that share a relationship can be grouped into a “bundle,” a “stack,” and/or a “deck” of cards. The terms group of cards, bundle of cards, stack of cards, and deck of cards may be used interchangeably herein. A group of cards can include any cards that can be considered to be related for a certain purpose, related based on criteria, and/or a related combination of criteria. For example, a collection of photos captured within a certain span of time can be represented as a photo bundle. As another example, a collection of messages (e.g. an instant messaging session, SMS/text-message exchange, or e-mail chain) can be represented as a message group. A bundle card can be constructed for display on the timeline that represents the bundle or group of cards and, in some cases, summarizes the bundle or group; e.g., shows thumbnail photos of photos in a photo bundle or a photo group. In some cases, data related to the card can be used to track relationship(s) used to create bundles or groups, e.g., a location associated with a card, an indication that the card is a photo, message, or other kind of card, a name of an application that created the card, etc. 
     By organizing objects, applications, and operations into cards, the UI can provide a relatively simple interface to a large collection of possible data sources. Further, by enabling operation on a collection of cards arranged in a natural fashion—according to time in one example—the wearer can readily locate and then utilize cards stored by the HMD. 
     B. Example Wearable Computing Devices 
     Systems and devices in which example embodiments can be implemented will now be described in greater detail. In general, an example system can be implemented in or can take the form of a wearable computer (also referred to as a wearable computing device). In an example embodiment, a wearable computer takes the form of or includes a head-mountable device (HMD). 
     An example system can also be implemented in or take the form of other devices, such as a mobile phone, among other possibilities. Further, an example system can take the form of non-transitory computer readable medium, which has program instructions stored thereon that are executable by a processor to provide the functionality described herein. An example system can also take the form of a device such as a wearable computer or mobile phone, or a subsystem of such a device, which includes such a non-transitory computer readable medium having such program instructions stored thereon. 
     An HMD can generally be any display device that is capable of being worn on the head and places a display in front of one or both eyes of the wearer. An HMD can take various forms such as a helmet or eyeglasses. As such, references to “eyeglasses” or a “glasses-style” HMD should be understood to refer to an HMD that has a glasses-like frame so that it can be worn on the head. Further, example embodiments can be implemented by or in association with an HMD with a single display or with two displays, which can be referred to as a “monocular” HMD or a “binocular” HMD, respectively. 
       FIG. 1A  illustrates a wearable computing system according to an example embodiment. In  FIG. 1A , the wearable computing system takes the form of a head-mountable device (HMD)  102  (which can also be referred to as a head-mounted display). It should be understood, however, that example systems and devices can take the form of or be implemented within or in association with other types of devices, without departing from the scope of the invention. As illustrated in  FIG. 1A , the HMD  102  includes frame elements including lens-frames  104 ,  106  and a center frame support  108 , lens elements  110 ,  112 , and extending side-arms  114 ,  116 . The center frame support  108  and the extending side-arms  114 ,  116  are configured to secure the HMD  102  to a user&#39;s face via a user&#39;s nose and ears, respectively. 
     Each of the frame elements  104 ,  106 , and  108  and the extending side-arms  114 ,  116  can be formed of a solid structure of plastic and/or metal, or can be formed of a hollow structure of similar material so as to allow wiring and component interconnects to be internally routed through the HMD  102 . Other materials can be possible as well. 
     One or more of each of the lens elements  110 ,  112  can be formed of any material that can suitably display a projected image or graphic. Each of the lens elements  110 ,  112  can also be sufficiently transparent to allow a user to see through the lens element. Combining these two features of the lens elements can facilitate an augmented reality or heads-up display where the projected image or graphic is superimposed over a real-world view as perceived by the user through the lens elements. 
     The extending side-arms  114 ,  116  can each be projections that extend away from the lens-frames  104 ,  106 , respectively, and can be positioned behind a user&#39;s ears to secure the HMD  102  to the user. The extending side-arms  114 ,  116  can further secure the HMD  102  to the user by extending around a rear portion of the user&#39;s head. Additionally or alternatively, for example, the HMD  102  can connect to or be affixed within a head-mounted helmet structure. Other configurations for an HMD are also possible. 
     The HMD  102  can also include an on-board computing system  118 , an image capture device  120 , a sensor  122 , and a finger-operable touch pad  124 . The on-board computing system  118  is shown to be positioned on the extending side-arm  114  of the HMD  102 ; however, the on-board computing system  118  can be provided on other parts of the HMD  102  or can be remotely positioned from the HMD  102  (e.g., the on-board computing system  118  could be wire- or wirelessly-connected to the HMD  102 ). The on-board computing system  118  can include a processor and memory, for example. The on-board computing system  118  can be configured to receive and analyze data from the image capture device  120  and the finger-operable touch pad  124  (and possibly from other sensory devices, user interfaces, or both) and generate images for output by the lens elements  110  and  112 . 
     The image capture device  120  can be, for example, a camera that is configured to capture still images and/or to capture video. In the illustrated configuration, image capture device  120  is positioned on the extending side-arm  114  of the HMD  102 ; however, the image capture device  120  can be provided on other parts of the HMD  102 . The image capture device  120  can be configured to capture images at various resolutions or at different frame rates. Many image capture devices with a small form-factor, such as the cameras used in mobile phones or webcams, for example, can be incorporated into an example of the HMD  102 . 
     Further, although  FIG. 1A  illustrates one image capture device  120 , more image capture devices can be used, and each can be configured to capture the same view, or to capture different views. For example, the image capture device  120  can be forward facing to capture at least a portion of the real-world view perceived by the user. This forward facing image captured by the image capture device  120  can then be used to generate an augmented reality where computer generated images appear to interact with or overlay the real-world view perceived by the user. 
     The sensor  122  is shown on the extending side-arm  116  of the HMD  102 ; however, the sensor  122  can be positioned on other parts of the HMD  102 . For illustrative purposes, only one sensor  122  is shown. However, in an example embodiment, the HMD  102  can include multiple sensors. For example, an HMD  102  can include sensors  102  such as one or more gyroscopes, one or more accelerometers, one or more magnetometers, one or more light sensors, one or more infrared sensors, and/or one or more microphones. Other sensing devices can be included in addition or in the alternative to the sensors that are specifically identified herein. 
     The finger-operable touch pad  124  is shown on the extending side-arm  114  of the HMD  102 . However, the finger-operable touch pad  124  can be positioned on other parts of the HMD  102 . Also, more than one finger-operable touch pad can be present on the HMD  102 . The finger-operable touch pad  124  can be used by a user to input commands. The finger-operable touch pad  124  can sense at least one of a pressure, position and/or a movement of one or more fingers via capacitive sensing, resistance sensing, or a surface acoustic wave process, among other possibilities. The finger-operable touch pad  124  can be capable of sensing movement of one or more fingers simultaneously, in addition to sensing movement in a direction parallel or planar to the pad surface, in a direction normal to the pad surface, or both, and can also be capable of sensing a level of pressure applied to the touch pad surface. In some embodiments, the finger-operable touch pad  124  can be formed of one or more translucent or transparent insulating layers and one or more translucent or transparent conducting layers. Edges of the finger-operable touch pad  124  can be formed to have a raised, indented, or roughened surface, so as to provide tactile feedback to a user when the user&#39;s finger reaches the edge, or other area, of the finger-operable touch pad  124 . If more than one finger-operable touch pad is present, each finger-operable touch pad can be operated independently, and can provide a different function. 
     In a further aspect, HMD  102  can be configured to receive user input in various ways, in addition or in the alternative to user input received via finger-operable touch pad  124 . For example, on-board computing system  118  can implement a speech-to-text process and utilize a syntax that maps certain spoken commands to certain actions. In addition, HMD  102  can include one or more microphones via which a wearer&#39;s speech can be captured. Configured as such, HMD  102  can be operable to detect spoken commands and carry out various computing functions that correspond to the spoken commands. 
     As another example, HMD  102  can interpret certain head-movements as user input. For example, when HMD  102  is worn, HMD  102  can use one or more gyroscopes and/or one or more accelerometers to detect head movement. The HMD  102  can then interpret certain head-movements as being user input, such as nodding, or looking up, down, left, or right. An HMD  102  could also pan or scroll through graphics in a display according to movement. Other types of actions can also be mapped to head movement. 
     As yet another example, HMD  102  can interpret certain gestures (e.g., by a wearer&#39;s hand or hands) as user input. For example, HMD  102  can capture hand movements by analyzing image data from image capture device  120 , and initiate actions that are defined as corresponding to certain hand movements. 
     As a further example, HMD  102  can interpret eye movement as user input. In particular, HMD  102  can include one or more inward-facing image capture devices and/or one or more other inward-facing sensors (not shown) that can be used to track eye movements and/or determine the direction of a wearer&#39;s gaze. As such, certain eye movements can be mapped to certain actions. For example, certain actions can be defined as corresponding to movement of the eye in a certain direction, a blink, and/or a wink, among other possibilities. 
     HMD  102  also includes a speaker  125  for generating audio output. In one example, the speaker could be in the form of a bone conduction speaker, also referred to as a bone conduction transducer (BCT). Speaker  125  can be, for example, a vibration transducer or an electroacoustic transducer that produces sound in response to an electrical audio signal input. The frame of HMD  102  can be designed such that when a user wears HMD  102 , the speaker  125  contacts the wearer. Alternatively, speaker  125  can be embedded within the frame of HMD  102  and positioned such that, when the HMD  102  is worn, speaker  125  vibrates a portion of the frame that contacts the wearer. In either case, HMD  102  can be configured to send an audio signal to speaker  125 , so that vibration of the speaker can be directly or indirectly transferred to the bone structure of the wearer. When the vibrations travel through the bone structure to the bones in the middle ear of the wearer, the wearer can interpret the vibrations provided by BCT  125  as sounds. 
     Various types of bone-conduction transducers (BCTs) can be implemented, depending upon the particular implementation. Generally, any component that is arranged to vibrate the HMD  102  can be incorporated as a vibration transducer. Yet further it should be understood that an HMD  102  can include a single speaker  125  or multiple speakers. In addition, the location(s) of speaker(s) on the HMD can vary, depending upon the implementation. For example, a speaker can be located proximate to a wearer&#39;s temple (as shown), behind the wearer&#39;s ear, proximate to the wearer&#39;s nose, and/or at any other location where the speaker  125  can vibrate the wearer&#39;s bone structure. 
       FIG. 1B  illustrates an alternate view of the wearable computing device illustrated in  FIG. 1A . As shown in  FIG. 1B , the lens elements  110 ,  112  can act as display elements. The HMD  102  can include a first projector  128  coupled to an inside surface of the extending side-arm  116  and configured to project a display  130  onto an inside surface of the lens element  112 . Additionally or alternatively, a second projector  132  can be coupled to an inside surface of the extending side-arm  114  and configured to project a display  134  onto an inside surface of the lens element  110 . 
     The lens elements  110 ,  112  can act as a combiner in a light projection system and can include a coating that reflects the light projected onto them from the projectors  128 ,  132 . In some embodiments, a reflective coating may not be used (e.g., when the projectors  128 ,  132  are scanning laser devices). 
     In alternative embodiments, other types of display elements can also be used. For example, the lens elements  110 ,  112  themselves can include: a transparent or semi-transparent matrix display, such as an electroluminescent display or a liquid crystal display, one or more waveguides for delivering an image to the user&#39;s eyes, or other optical elements capable of delivering an in focus near-to-eye image to the user. A corresponding display driver can be disposed within the frame elements  104 ,  106  for driving such a matrix display. Alternatively or additionally, a laser or LED source and scanning system could be used to draw a raster display directly onto the retina of one or more of the user&#39;s eyes. Other possibilities exist as well. 
       FIG. 1C  illustrates another wearable computing system according to an example embodiment, which takes the form of an HMD  152 . The HMD  152  can include frame elements and side-arms such as those described with respect to  FIGS. 1A and 1B . The HMD  152  can additionally include an on-board computing system  154  and an image capture device  156 , such as those described with respect to  FIGS. 1A and 1B . The image capture device  156  is shown mounted on a frame of the HMD  152 . However, the image capture device  156  can be mounted at other positions as well. 
     As shown in  FIG. 1C , the HMD  152  can include a single display  158  which can be coupled to the device. The display  158  can be formed on one of the lens elements of the HMD  152 , such as a lens element described with respect to  FIGS. 1A and 1B , and can be configured to overlay computer-generated graphics in the user&#39;s view of the physical world. The display  158  is shown to be provided in a center of a lens of the HMD  152 , however, the display  158  can be provided in other positions, such as for example towards either the upper or lower portions of the wearer&#39;s field of view. The display  158  is controllable via the computing system  154  that is coupled to the display  158  via an optical waveguide  160 . 
       FIG. 1D  illustrates another wearable computing system according to an example embodiment, which takes the form of a monocular HMD  172 . The HMD  172  can include side-arms  173 , a center frame support  174 , and a bridge portion with nosepiece  175 . In the example shown in  FIG. 1D , the center frame support  174  connects the side-arms  173 . The HMD  172  does not include lens-frames containing lens elements. The HMD  172  can additionally include a component housing  176 , which can include an on-board computing system (not shown), an image capture device  178 , and a button  179  for operating the image capture device  178  (and/or usable for other purposes). Component housing  176  can also include other electrical components and/or can be electrically connected to electrical components at other locations within or on the HMD. HMD  172  also includes a BCT  186 . 
     The HMD  172  can include a single display  180 , which can be coupled to one of the side-arms  173  via the component housing  176 . In an example embodiment, the display  180  can be a see-through display, which is made of glass and/or another transparent or translucent material, such that the wearer can see their environment through the display  180 . Further, the component housing  176  can include the light sources (not shown) for the display  180  and/or optical elements (not shown) to direct light from the light sources to the display  180 . As such, display  180  can include optical features that direct light that is generated by such light sources towards the wearer&#39;s eye, when HMD  172  is being worn. 
     In a further aspect, HMD  172  can include a sliding feature  184 , which can be used to adjust the length of the side-arms  173 . Thus, sliding feature  184  can be used to adjust the fit of HMD  172 . Further, an HMD can include other features that allow a wearer to adjust the fit of the HMD, without departing from the scope of the invention. 
       FIGS. 1E to 1G  are simplified illustrations of the HMD  172  shown in  FIG. 1D , being worn by a wearer  190 . As shown in  FIG. 1F , when HMD  172  is worn, BCT  186  is arranged such that when HMD  172  is worn, BCT  186  is located behind the wearer&#39;s ear. As such, BCT  186  is not visible from the perspective shown in  FIG. 1E . 
     In the illustrated example, the display  180  can be arranged such that when HMD  172  is worn, display  180  is positioned in front of or proximate to a user&#39;s eye when the HMD  172  is worn by a user. For example, display  180  can be positioned below the center frame support and above the center of the wearer&#39;s eye, as shown in  FIG. 1E . Further, in the illustrated configuration, display  180  can be offset from the center of the wearer&#39;s eye (e.g., so that the center of display  180  is positioned to the right and above of the center of the wearer&#39;s eye, from the wearer&#39;s perspective). 
     Configured as shown in  FIGS. 1E to 1G , display  180  can be located in the periphery of the field of view of the wearer  190 , when HMD  172  is worn. Thus, as shown by  FIG. 1F , when the wearer  190  looks forward, the wearer  190  can see the display  180  with their peripheral vision. As a result, display  180  can be outside the central portion of the wearer&#39;s field of view when their eye is facing forward, as it commonly is for many day-to-day activities. Such positioning can facilitate unobstructed eye-to-eye conversations with others, as well as generally providing unobstructed viewing and perception of the world within the central portion of the wearer&#39;s field of view. Further, when the display  180  is located as shown, the wearer  190  can view the display  180  by, e.g., looking up with their eyes only (possibly without moving their head). This is illustrated as shown in  FIG. 1G , where the wearer has moved their eyes to look up and align their line of sight with display  180 . A wearer might also use the display by tilting their head down and aligning their eye with the display  180 . 
       FIG. 2A  illustrates a schematic drawing of a computing device  210  according to an example embodiment. In an example embodiment, device  210  communicates using a communication link  220  (e.g., a wired or wireless connection) to a remote device  230 . The device  210  can be any type of device that can receive data and display information corresponding to or associated with the data. For example, the device  210  can be a heads-up display system, such as the head-mounted devices  102 ,  152 , or  172  described with reference to  FIGS. 1A to 1G . 
     Thus, the device  210  can include a display system  212  including a processor  214  and a display  216 . The display  216  can be, for example, an optical see-through display, an optical see-around display, or a video see-through display. The processor  214  can receive data from the remote device  230 , and configure the data for display on the display  216 . The processor  214  can be any type of processor, such as a micro-processor or a digital signal processor, for example. 
     The device  210  can further include on-board data storage, such as memory  218  coupled to the processor  214 . The memory  218  can store software that can be accessed and executed by the processor  214 , for example. 
     The remote device  230  can be any type of computing device or transmitter including a laptop computer, a mobile telephone, or tablet computing device, etc., that is configured to transmit data to the device  210 . The remote device  230  and the device  210  can contain hardware to enable the communication link  220 , such as processors, transmitters, receivers, antennas, etc. 
     Further, remote device  230  can take the form of or be implemented in a computing system that is in communication with and configured to perform functions on behalf of client device, such as computing device  210 . Such a remote device  230  can receive data from another computing device  210  (e.g., an HMD  102 ,  152 , or  172  or a mobile phone), perform certain processing functions on behalf of the device  210 , and then send the resulting data back to device  210 . This functionality can be referred to as “cloud” computing. 
     In  FIG. 2A , the communication link  220  is illustrated as a wireless connection; however, wired connections can also be used. For example, the communication link  220  can be a wired serial bus such as a universal serial bus or a parallel bus. A wired connection can be a proprietary connection as well. The communication link  220  can also be a wireless connection using, e.g., Bluetooth® radio technology, communication protocols described in IEEE 802.11 (including any IEEE 802.11 revisions), Cellular technology (such as GSM, CDMA, UMTS, EV-DO, WiMAX, or LTE), or Zigbee® technology, among other possibilities. The remote device  230  can be accessible via the Internet and can include a computing cluster associated with a particular web service (e.g., social-networking, photo sharing, address book, etc.). 
     C. Example Image Projection 
       FIG. 2B  shows an example projection of UI elements described herein via an image  280  by an example head-mountable device (HMD)  252 , according to an example embodiment. Other configurations of an HMD can also be used to present the UI described herein via image  280 .  FIG. 2B  shows wearer  254  of HMD  252  looking at an eye of person  256 . As such, wearer  254 &#39;s gaze, or direction of viewing, is along gaze vector  260 . A horizontal plane, such as horizontal gaze plane  264  can then be used to divide space into three portions: space above horizontal gaze plane  264 , space in horizontal gaze plane  264 , and space below horizontal gaze plane  264 . In the context of projection plane  276 , horizontal gaze plane  260  appears as a line that divides projection plane into a subplane above the line of horizontal gaze plane  260 , a subplane below the line of horizontal gaze plane  260 , and the line where horizontal gaze plane  260  intersects projection plane  276 . In  FIG. 2B , horizontal gaze plane  264  is shown using dotted lines. 
     Additionally, a dividing plane, indicated using dividing line  274  can be drawn to separate space into three other portions: space to the left of the dividing plane, space on the dividing plane, and space to right of the dividing plane. In the context of projection plane  276 , the dividing plane intersects projection plane  276  at dividing line  274 . Thus, the dividing plane divides projection plane into: a subplane to the left of dividing line  274 , a subplane to the right of dividing line  274 , and dividing line  274 . In  FIG. 2B , dividing line  274  is shown as a solid line. 
     Humans, such wearer  254 , when gazing in a gaze direction, can have limits on what objects can be seen above and below the gaze direction.  FIG. 2B  shows the upper visual plane  270  as the uppermost plane that wearer  254  can see while gazing along gaze vector  260 , and shows lower visual plane  272  as the lowermost plane that wearer  254  can see while gazing along gaze vector  260 . In  FIG. 2B , upper visual plane  270  and lower visual plane  272  are shown using dashed lines. 
     The HMD can project an image for view by wearer  254  at some apparent distance  262  along display line  282 , which is shown as a dotted and dashed line in  FIG. 2B . For example, apparent distance  262  can be 1 meter, four feet, infinity, or some other distance. That is, HMD  252  can generate a display, such as image  280 , which appears to be at the apparent distance  262  from the eye of wearer  254  and in projection plane  276 . In this example, image  280  is shown between horizontal gaze plane  264  and upper visual plane  270 ; that is image  280  is projected above gaze vector  260 . In this example, image  280  is also projected to the right of dividing line  274 . As image  280  is projected above and to the right of gaze vector  260 , wearer  254  can look at person  256  without image  280  obscuring their general view. In one example, the display element of the HMD  252  is translucent when not active (i.e. when image  280  is not being displayed), and so the wearer  254  can perceive objects in the real world along the vector of display line  282 . 
     Other example locations for displaying image  280  can be used to permit wearer  254  to look along gaze vector  260  without obscuring the view of objects along the gaze vector. For example, in some embodiments, image  280  can be projected above horizontal gaze plane  264  near and/or just above upper visual plane  270  to keep image  280  from obscuring most of wearer  254 &#39;s view. Then, when wearer  254  wants to view image  280 , wearer  254  can move their eyes such that their gaze is directly toward image  280 . 
     D. An Example User Interface for an HMD 
       FIGS. 3 through 13B  collectively describe aspects of an example user interface for an HMD such as discussed above at least in the context of  FIGS. 1A through 2B . The HMD can be configured with a user interface (UI) controller receiving inputs from at least two user interfaces: a touch-based UI and a voice-based UI. The touch-based UI can include a touch pad and a button, configured to receive various touches, such as one-finger swipes in various directions, two-finger or multi-finger swipes in various directions, taps, button presses of various durations, and button releases. 
     Once a touch is received, the touch-based UI can report the touch; e.g., a “swipe forward” or “tap” to the HMD, or in some cases, to a component of the HMD such as a UI controller. In other embodiments, the HMD can act as the UI controller. As described herein, the HMD includes any necessary components, such as but not limited to one or more UI controllers, which are configured to perform and control the UI operations described herein. 
     The voice-based UI can include a microphone configured to receive various words, including commands, and to report the received words; e.g., “Call Mom,” to the HMD. In some embodiments, the HMD can include a gaze-based UI that is configured to detect duration and/or direction of one or more gazes of a wearer of the HMD. For example, the gaze-based UI can be configured to detect “dwell time” or how long the wearer gazes in a fixed direction, the direction of the gaze, a rate of change of the gaze, and additional information related to wearer gazes. In some cases, the HMD can generate audible outputs; e.g., tones, words, songs, etc., that can be heard by the wearer via headphones, speakers, or bone conduction devices of the HMD. 
     The HMD can generate “cards,” also referred to as screens or images, which are capable of occupying the full display of the HMD when selected. One card is a home card that is the first card displayed when UI is activated, for example shortly after HMD powers up or when the HMD wakes from a sleep or power-saving mode.  FIG. 3  shows an example home card  300  of an example user interface, according to an example embodiment. Home card  300  includes application status indicators  310 , device status indicators  312 , hint  314  and a clock shown in large numerals indicating the present time in the center of home card  300 . Application status indicators  310  can indicate which application(s) are operating on the HMD. As shown in  FIG. 3 , application status indicators  310  include camera and Y-shaped road icons to respectively indicate operation of a camera application and a navigation application. Such indicators can remind the wearer what applications or processes are presently running and/or consuming power and/or processor resources of the HMD. 
     Device status indicators  312  can indicate which device(s) are operating on the HMD and HMD status. As shown in  FIG. 3 , device status indicators  312  include icons for a wireless network and a Bluetooth network, respectively, that indicate the HMD is presently configured for communication via a wireless network and/or a Bluetooth network. In one embodiment, the HMD may not present device status indicators  312  on home card  300 . 
     Hint  314  is shown in  FIG. 3  as “ok glass.” Hint  314  is shown in quotes to indicate that the hint is related to the voice-based UI of the HMD. In some embodiments, hint  314  can be related to the touch-based UI of the HMD. The words in hint  314  illustrated as “ok glass” indicate that a wearer should say the words “ok glass” to activate the voice-based UI of the HMD. In other words, “ok glass” in this instance is a word (that can also be referred to as “a hotword”) that triggers activation of a voice-based UI. Other hotwords can also be used. 
     As also indicated in the lower portion of  FIG. 3 , if hint  314  is used successfully a number, e.g., 5, of times, the HMD can remove hint  314  from being displayed on home card  110 . However, if the HMD has a gaze-based UI and detects that a dwell time of the wearer on the home card exceeds a threshold, such as a 30-second threshold, the HMD can add hint  314  back to home card  110  to remind the wearer about specific words, e.g., ok glass, used to activate the voice-based UI. In one embodiment, the hotword presented as hint  314  on home card  300  can be updated to make the user aware of other functionality of the HMD, or to suggest queries or actions based on the HMD&#39;s current geographic location or situational context. 
     The UI can accept as inputs certain operations performed using the touch-based UI. The UI can receive these operations and responsively perform actions to enable the wearer to interact with the HMD. These operations can be organized into tiers.  FIG. 4  lists example operations of a multi-tiered user model  400  for a user interface for a head-mountable device (HMD), according to an example embodiment. 
     As shown in  FIG. 4 , multi-tiered user model  400  has three tiers: basic, intermediate, and advanced. The basic tier provides the smallest number of operations of any tier of multi-tiered user model  400 . The intermediate tier includes all operations provided by the basic tier, along with additional operations not provided by the basic tier. Similarly, the advanced tier includes all operations provided by the basic and intermediate tiers, along with additional operations not provided by either the basic tier or intermediate tier. 
       FIG. 4  shows that the basic tier of multi-tiered user model  400  provides tap, swipe forward, swipe backward, voice, and camera button press operations. A tap operation can involve a single physical tap—that is, one quick, slight strike with one or more fingers on the touch pad of the touch-based UI. A swipe forward operation, sometimes termed a swipe right, can involve a movement forward by one or more fingers touching the touch pad, where forward is the general direction from the wearer&#39;s ear toward the wearer&#39;s eye when the wearer has the HMD on. A swipe backward operation, sometimes termed a “swipe left,” can involve a movement backward by one or more fingers touching the touch pad, where backward is the general direction from the wearer&#39;s eye toward the wearer&#39;s ear when the wearer has the HMD on. A “swipe down” operation can involve a downward movement by one or more fingers touching the touch pad, where downward is the general direction from the top of the wearer&#39;s head toward the wearer&#39;s neck when the wearer has the HMD on. 
     While example embodiments in this description make reference to particular directions of touchpad input such as up, down, left, right, it should be understood that these are exemplary and that embodiments where certain operations can be triggered via different input directions are contemplated. 
     In one embodiment, the physical actions used by the wearer to perform some or all of the herein-described operations can be customized; e.g., by the wearer and/or other entity associated with the HMD. For example, suppose the wearer prefers to perform a physical action of a “double-tap”—that is, one physical tap quickly followed by a second physical tap—rather than the above-mentioned single physical tap, to perform a tap operation. In this embodiment, the wearer and/or other entity could configure the HMD to recognize a double-tap as a tap operation, such as by training or setting the HMD to associate the double-tap with the tap operation. As another example, suppose that the wearer would like to interchange the physical operations to perform swipe forward and backward operations; e.g., the swipe forward operation would be performed using a physical action described above as a swipe left and the swipe backward operation would be performed using a physical action described above as a swipe right. In this embodiment, the wearer could configure the HMD to recognize a physical swipe left as a swipe forward operation and physical swipe right as a swipe backward operation. Other customizations are possible as well; e.g., using a sequence of swipes to carry out the tap operation. 
     The tap operation can select a currently visible card. The swipe forward operation can remove the currently visible card from display and select a next card for display. The swipe backward operation can remove the currently visible card from display and select a previous card for display. 
     The swipe down operation can, depending on context, act to go back, go home, or sleep. Going back can remove the currently visible card from display and display a previously-visible card for display. For example, the previously-visible card can be the card that most recently viewed; e.g. if card A is currently visible and card B is previously-viewed card, then the swipe down operation can remove card A from visibility and display card B. Going home can replace the currently visible card from display and display the home card. Sleeping can cause part of the HMD, e.g., the display, or all of the HMD to be deactivated. 
     A voice operation can provide access to a voice menu of operations. A camera button press can instruct the HMD to take a photo using a camera associated with and/or part of the HMD. 
       FIG. 4  shows that the intermediate tier of multi-tiered user model  400  provides tap, swipe forward, swipe backward, voice, and camera button press operations as described above in the context of the basic tier. Also, the intermediate tier provides camera button long press, two finger swipe forward, two finger swipe backward, and two finger swipe down operations. 
     The camera button long press operation can instruct the HMD to provide a capture menu for display and use. The capture menu can provide one or more operations for using the camera associated with HMD. 
     The two finger swipe forward operation removes the currently visible card from display and selects a next card for display using a “zoomed scroll.” The two finger swipe forward operation removes the currently visible card from display and selects the next card for display using a zoomed scroll. Zoomed scrolls are discussed in more detail in the context of at least  FIG. 6A . The two finger swipe down causes the HMD to sleep at this position in a timeline. 
       FIG. 4  shows that the advanced tier of multi-tiered user model  400  provides tap, swipe forward, swipe backward, voice, and camera button press operations as described above in the context of the basic tier, as well as camera button long press, two finger swipe forward, two finger swipe backward, and two finger swipe down operations described above in the context of the intermediate tier. The advanced tier also provides one-finger press-and-holds, two-finger press-and-holds, and nudge operations. 
     The one-finger press-and-hold operation zooms, or expands, the display of the current card, or content related to the current card, starting when the wearer presses on the touch-based UI and continues to zoom as long as the wearer “holds” or keeps pressing on the touch-based UI. 
     The two-finger press-and-hold can provide a “clutch” operation, which can be performed by pressing on the touch-based UI in two separate spots using two fingers and holding the fingers in their respective positions on the touch-based UI. After the fingers are held in position on the touch-based UI, the clutch operation is engaged. In some embodiments, the HMD recognizes the clutch operation only after the fingers are held for at least a threshold period of time; e.g., one second. The clutch operation will stay engaged as long as the two fingers remain on the touch based UI. Clutch operations are discussed in more detail below in the context of at least  FIGS. 6B and 6C . 
     The nudge operation can be performed using a short, slight nod of the wearer&#39;s head. For example, the HMD can be configured with accelerometers or other motion detectors that can detect the nudge and provide an indication of the nudge to the HMD. Upon receiving indication of a nudge, the HMD can toggle an activation state of the HMD. That is, if the HMD is active (e.g., displaying a card on the activated display) before the nudge, the HMD can deactivate itself (e.g., turn off the display) in response. Alternatively, if the HMD is inactive before the nudge but is active enough to detect nudges; e.g., within two or a few seconds of notification of message arrival, the HMD can activate itself in response. 
     By way of further example, in one scenario, the HMD is powered on with the display inactive. In response to the HMD receiving a new text message, an audible chime can be emitted by the HMD. Then, if the wearer nudges within a few seconds of the chime, the HMD can activate and present a card with the content of the text message. If, from the activated state, the user nudges again, the display will deactivate. Thus, in this example, the user can interact with the device in a completely hands-free manner. 
     As mentioned above, the UI maintains a timeline or ordered sequence of cards that can be operated on using the operations described in  FIG. 4  immediately above.  FIG. 5A  shows a scenario  500  of example timeline interactions, according to an example embodiment. 
     Scenario  500  begins with home card  502  being displayed by an HMD worn by a wearer. Home card  502  and cards  520   a - 520   c  can be arranged as a “timeline” or ordered sequence of cards. In the example shown in  FIG. 5A , each card in timeline  510  has a specific time associated with the card. The timeline can be ordered based on the specific time associated with each card. In some cases, the specific time can be “now” or the present time. For example, home card  502  can be associated with the specific time of now. In other cases, the time can be a time associated with an event leading to the card. For example,  FIG. 5A  shows that card  520   a  represents a photo taken at a time 2 hours ago. Then, card  520   a  can be associated with the specific time of 1:28, which is 2 hours before the present time of 3:28 shown on home card  500 . 
     Cards  520   b - 520   f  represent current cards, or cards associated with the specific time of now, or upcoming cards, or cards associated with a future time. For example, card  520   b  is a current card that includes an image currently generated by a camera associated with the HMD, card  520   c  is a current card that includes an image of a “hangout” or video conference call currently in-progress generated by an application of the HMD, card  520   d  is a current card that includes an image and text currently generated by a navigation application/process presently running on the HMD, card  520   e  is a current card that includes images and text currently generated by a weather application of the HMD, and  520   f  is an upcoming card that includes images and text generated by a calendar application of the HMD indicating an appointment for “Lunch with Monica Kim” in “2 hours.” 
     In scenario  500 , the HMD can enable navigation of the time line using swipe operations. For example, starting at home card  502 , a swipe backward operation can cause the HMD to select and display a previous card, such as card  520   a , and a swipe forward operation can cause the HMD to select and display a next card, such as card  520   b . Upon displaying card  520   b , the swipe forward operation can cause the HMD to select and display the previous card, which is home card  502 , and the swipe backward operation can cause the HMD to select and display the next card, which is card  520   c.    
     In scenario  500 , there are no cards in timeline  510  that are previous to card  520   a . In one embodiment, the timeline is represented as a circular timeline. For example, in response to a swipe backward operation on card  520   a  requesting a previous card for display, the HMD can select  520   f  for (re)display, as there are no cards in timeline  510  that are after card  520   f  during scenario  500 . Similarly, in response to a swipe forward operation on card  520   f  requesting a next card for display, the HMD can select  520   a  for (re)display, as there are no cards in timeline  510  that are after card  520   f  during scenario  500 . 
     In another embodiment, instead of a circular representation of the timeline, when the user navigates to the end of the timeline, a notification is generated to indicate to the user that there are no additional cards to navigate to in the instructed direction. Examples of such notifications could include any of or a combination of the following: a visual effect, an audible effect, a glowing effect on the edge of the card, a three dimensional animation twisting the edge of the card, a sound (e.g. a click), a textual or audible message indicating that the end of the timeline has been reached (e.g. “there are no cards older than this”). Alternatively, in one embodiment, an attempt by the user to navigate past a card in a direction where there are no additional cards could result in no effect, i.e. swiping right on card  520   a  results in no perceptible change to the display or card  520   a.    
     While displaying home card  502 , a wearer of the HMD can recite or utter a hotword, for example the words “ok glass” to activate the voice-based interface of the HMD. In response, the HMD can display card  530  that lists some of the commands that can be uttered by the wearer to interact with the voice-based interface.  FIG. 5A  shows example commands as “Google” to perform a search query, “navigate to” to find directions to a location, “take a photo” to capture an image using a camera associated with the HMD, “record a video” to capture a sequence of images and/or associated sounds, using a camera and/or a microphone associated with the HMD, and “send a message” to generate and send an e-mail, SMS message, instant message, or some other type of message. 
     While displaying card  530 , the wearer can utter something in response, which can lead to voice interactions with the UI. The commands capable of triggering voice interactions are not necessarily limited to those presented on card  530  at the time the utterance is received. For example, as the user dwells on card  530 , additional commands can be presented for other features. Further, such commands presented on card  530  can change over time through further use of the HMD, or can be remotely updated to surface additional features or content of the HMD. Still further, similar to the frequent contact aspects described herein, commands for frequently used functions of the HMD can be presented on card  530 . As such, these commands can change over time based on use of the HMD by the wearer. 
     In some examples, timelines can become lengthy. The UI provides operations for speedy use of the UI, such as two-fingered swipes and clutches, although other gestures to invoke such navigation operations are possible.  FIG. 6A  shows an example of using a two-fingered swipe on a touch-based UI of an HMD for zoomed scrolling, according to an example embodiment. 
       FIG. 5B  shows scenario  584  using a multi-timeline display, according to an example embodiment. Scenario  584  begins with a wearer of an HMD using View A, shown at the top of  FIG. 5B , that can be generated by the HMD to observe home card  588   a  displayed in single-card view  586 . In scenario  584 , a wearer of an HMD can switch from single-card view  586  into a multi-timeline view using a clutch operation. In other scenarios, a different operation or operations than a clutch can be performed to switch into the multi-timeline view. 
     In scenario  584 , multiple cards of main timeline  588  can be displayed simultaneously upon entering the multi-timeline view. View B of  FIG. 5B , shown just below View A, illustrates a multi-timeline view and shows three cards  588   a ,  588   b , and  588   c  of main timeline  588  in a linear arrangement. Card  588   a  is a home card for main timeline  588 , card  588   b  is a card representing an “Email” from “LunchPal” that arrived “5 min ago,” and card  588   c  is a bundle card that shows a number of thumbnail images related to a bundle of contacts called “Friends.” 
     In scenario  584 , card  588   a  was shown in while in single-user view  586  and in an initial multi-timeline view. In some scenarios, the initial multi-timeline view can be centered on the card shown in a previous single-card view; e.g., home card  588   a . In other scenarios, multiple timelines can be displayed as part of the initial multi-timeline view; for example, main timeline  588  can be accompanied by a one or more timelines showing card representing one or more contacts, photos, previous events, future events, and/or other cards. 
     In scenario  584 , the wearer of the HMD can select a card for use by controlling a selection region. A given card, such as card  588   b , can be selected when the selection region is aligned with the given card. In this context, the selection region can be aligned with a given card in a display when the selection region is placed over the given card in the display, the selection region substantially overlaps the given card in the display, and/or a UI action (e.g., a tap of a touchpad, a click of a mouse, a key press) is performed when the selection region overlaps the given card in the display. Other techniques for aligning a selection region and a given card are possible as well. In some embodiments, the selection region substantially overlaps the given card when at least 50% of the selection region overlaps the given card in the display. In some embodiments, the HMD can be configured to detect head movements and the selection region can be moved using the head movements. 
     In scenario  584 , the wearer of the HMD selects card  588   b  and, after the selection of card  588   b , View C can be generated, which is shown below and to the left of View B in  FIG. 5B . View C shows card  588   b  of main timeline  588  and a linear arrangement of three action cards  590   a ,  590   b , and  590   c  shown above card  588   b ; that is, View C shows multiple linear arrangements simultaneously. As shown in View C, the linear arrangement of action cards starts with card  590   a  that is directly above selected card  588   b , and the linear arrangement of action cards is adjacent to, above, and parallel to main timeline  588 . Card  588   a  is shown in View C as greyed out to indicate that card  588   a  is not selected. 
     Upon selection of action card  590   a  to “View All,” the wearer can view the e-mail represented by card  588   b . Selection of action card  590   b  to “Share” can enable the wearer to share; e.g., reply to, forward, post to a website, etc., the e-mail represented by card  588   b . Selection of action card  590   c  to “Delete” can permit the wearer to delete the e-mail represented by card  588   b.    
     In scenario  584 , the wearer selects card  590   a  to view all of the e-mail represented by card  588   b . After selection of card  590   a , the content of the e-mail is shown using three content cards  592   a ,  592   b , and  592   c  shown in View D as adjacent to and above selected card  590   a . View D is shown directly to the right of View C in  FIG. 5B . 
     View D also shows that the linear arrangement of contact cards begins with card  592   a , which is shown directly above selected card  592   a . View D does not show unselected action cards  590   b  and  590   c ; in some embodiments, unselected cards can be displayed. In particular scenarios, unselected but displayed card can be displayed in a visually distinct manner to indicate non-selection; e.g., shown with a grey background as for card  588   a  in View C. 
     Scenario  584  continues with the wearer of the HMD manipulating the selection region to return to the main timeline  588  and select card  588   c  as shown in View E.  FIG. 5B  shows View E below and to the left of View D. As mentioned above, card  588   c  is a bundle card representing a group of related cards; in this example, a group of contact cards. Each contact card can have an indication that the card is a contact card. In some embodiments, card represented by bundle card  588   c  can have an indication that the card is in the “Friends” bundle of cards/contacts. As such, the HMD can determine cards in the “Friends” bundle by searching for each card having an indication that the card is in the “Friends” group of cards. 
     Upon selection of card  588   c , the HMD can generate View F, which shows contact cards  594   a  and  594   b  of the “Friends” bundle displayed the linear arrangement with main timeline  588 . View F is shown in  FIG. 5B  directly below View E. Bundle card  588   b  is shown by View F as remaining in the linear arrangement with main timeline  588 . In some scenarios, contact cards  594   a  and  594   b , as well as additional cards in the “Friends” bundle can be shown in a linear arrangement adjacent to the linear arrangement showing a selected bundle card; e.g., card  588   c . In other scenarios, upon selection of bundle card  588   c , bundle card  588   c  is no longer displayed; rather, the bundle card can be considered to be replaced by the content of the bundle. 
     To speed movement in selecting next card(s) in the timeline, a wearer can swipe forward with two fingers, as shown in  FIG. 6A , to perform a zoomed scroll to a next card. Similarly, to speed movement in selecting previous card(s) in the timeline, a wearer can swipe backward with two fingers, as also shown in  FIG. 6 , to perform a zoomed scroll to a previous card. 
     Upon receiving a UI operation for a zoomed scroll, for example, a two-fingered swipe forward, a reduced-size view of cards can be displayed in the resulting timeline  610 . That is, as shown in  FIG. 6A , multiple cards can be shown in example display  612  generated by the HMD. A swipe or drag operation associated with the zoomed scroll can move content faster, e.g., 4 times faster, than when performing a regular swipe or drag operation. Inertial free scrolling can be performed as part of zoomed scrolling. After the zoomed scroll completes, the focus for the UI is on card  614  of timeline  610 .  FIG. 6A  shows card  614  outlined using a thick dashed line in the center of display  612 . 
     A timeline that has been released after the zoomed scroll can stay zoomed out, or can continue with reduced image views, until a minimum velocity threshold for the timeline is reached. After the minimum velocity threshold is reached, display  612  can be instructed to zoom to the card that is closest to the center of display  612 ; e.g., display  612  can zoom to card  614 . That is, the HMD can show card  614  as large as possible within display  612 . 
     Additional techniques for rapid movement within a timeline and between timelines can be provided by the UI. For example, a clutch operation can lead to generation and display of a multi-card display, such as shown in  FIG. 6B , or a multi-timeline display, such as shown in  FIG. 6C . Navigation within the multi-card display and/or multi-timeline display can, in some embodiments, be performed using head movements. In other embodiments, the multi-card display or multi-timeline display in toto can be focused on, or displayed by the HMD. Thus, to aid navigation, a sub-focus can be implemented to highlight a card or a timeline within a multi-card or multi-timeline display. 
       FIG. 6B  shows a scenario  620  for using clutch operation  642  to generate a multi-card display  634   a , according to an example embodiment. Scenario  620  begins with an HMD having timeline  630  with cards  630   a  through  630   g , and with a focus on card  630   d . During scenario  620 , prior to clutch  642 , the HMD displays cards in the timeline using a single-card view, while solely displaying a focused-upon card. As the focus is on card  630   d , which  FIG. 6  shows as a photo of a woman&#39;s face, the HMD displays a single-card view of card  630   d.    
     Scenario  620  continues with a wearer of the HMD performing clutch operation  642  using the touch-based UI of the HMD. A clutch operation can involve pressing on the touch-based UI of the HMD using two fingers and holding the two-finger press until the HMD recognizes the clutch operation  642  has been performed. Other gestures, techniques, inputs or time thresholds can be used to trigger the clutch operation. For example, in certain embodiments, a three-finger gesture or a voice-action could be used to engage and/or disengage the clutch operation. 
     Upon recognition of clutch operation  642 , in scenario  620 , the HMD can generate and display multi-card display  634   a , which is shown in an expanded view as multi-card display  634   b . In some embodiments, the HMD can focus on the entire multi-card display  634   a  using focus  636 . In other embodiments, the HMD can focus a subset of cards, such as but not limited to, a single card, a row of cards, a column of cards, a block of cards, or some other selection of cards, within multi-card display  634   a  using sub-focus  638 . For example, in scenario  620 , the HMD is configured to display sub-focus  638  on a single card. In some embodiments, the sub-focus can remain on one or more cards at or near the center of the display. 
     As shown in  FIG. 6B  using expanded multi-card display  634   b , the multi-card display shows nine cards: cards  630   a  through  630   g  of timeline  630  and two other cards  640   a  and  640   b  not shown as part of timeline  630 . The wearer of the HMD can navigate around multi-card display  634   a ,  634   b  using head movements, such as moving the wearer&#39;s head up, down, left, and/or right. In some embodiments, gaze tracking can be used in place of or in addition to head movements for navigating around multi-card display  634   a ,  634   b  and/or multi-timeline display  664   a ,  664   b.    
     In scenario  620 , “wrap-around” movements, or moving off the end of a row or column to the respective other end of the row or column, are enabled. Then, in response to respective movements upward, downward, leftward, or rightward by the head of the wearer, the sub-focus  638  can move from card  630   d , as shown in  FIG. 6B , to respective cards  630   a ,  630   g ,  630   f , or  630   e . In particular embodiments, wrap-around can be inhibited, so moving the wearer&#39;s head leftward will not move sub-focus  638  from card  630   d  to card  630   f , but rather sub-focus  638  will stay on card  630   d  or move to the left-end of the middle row. 
     In some embodiments, in response to respective movements diagonally up-and-left, up-and-right, down-and-left, and down-and-right by the head of the wearer, the sub-focus  638  can move from card  630   d , as shown in  FIG. 6B , to respective cards  630   c ,  630   b ,  640   b , or  640   c . Other types of head movements and/or UI operations can be used as well or instead with multi-card display  634   a ,  634   b , including but not limited to head movements and/or UI operations that move the focus faster than and/or slower than one card at a time, zooming in and out, reshaping sub-focus  638 , selecting card(s), and deselecting card(s). 
     In some embodiments, sub-focus  638  may not be used. For example, in these embodiments, a leftward head movement can move each of cards  630   b ,  630   c ,  630   e ,  630   f ,  640   a , and  640   b  to the left by one card and bring in new cards to the “right” of these cards (new cards not shown in  FIG. 6B ) on to multi-card displays  634   a  and  634   b . The new cards can be displayed in the respective positions of card  630   c ,  630   f , and  640   b , and remove cards  630   a ,  630   d , and  630   g  from multi-card display  634   a  and  634   b . Also, a rightward head movement can move each of cards  630   a ,  630   b ,  630   d ,  630   e ,  630   g , and  640   a  to the right by one card, bring in new cards to the “right” of these cards (not shown in  FIG. 4 ) on to multi-card displays  634   a  and  634   b . The new cards can be displayed in the respective positions of card  630   a ,  630   d , and  640   g , and remove cards  630   c ,  630   f , and  640   b  multi-card displays  634   a  and  634   b.    
     In these embodiments, an upward head movement can: (1) bring a new row of cards considered to be “above” the top row of cards; e.g., cards in the positions of cards  630   a ,  630   b ,  630   c  of multi-card displays  634   a  and  634   b , (2) display the new row of cards on the top row of multi-card displays  634   a  and  634   b , (3) move the top row of cards down to be displayed as the middle row of cards; e.g. display cards  630   a ,  630   b , and  630   c  in the positions of cards  630   d ,  630   e , and  630   f  of multi-card displays  634   a  and  634   b , (4) move the middle row of cards down to the bottom row of cards e.g. display cards  630   d ,  630   e , and  630   f  in the positions of cards  630   g ,  640   a , and  640   b  of multi-card displays  634   a  and  634   b , thus removing the bottom row of cards; e.g., cards  630   g ,  640   a , and  640   b , from view on multi-card displays  634   a  and  634   b.    
     In these embodiments, a downward head movement can: (1) bring a new row of cards considered to be “below” the bottom row of cards of multi-card displays  634   a  and  634   b , (2) display the new row of cards on the bottom row of multi-card displays  634   a  and  634   b , (3) move the bottom row of cards up to be displayed as the middle row of cards; e.g. display cards  630   g ,  640   a , and  640   b  in the positions of cards  630   d ,  630   e , and  630   f  of multi-card displays  634   a  and  634   b , (4) move the middle row of cards up to the top row of cards e.g. display cards  630   d ,  630   e , and  630   f  in the positions of cards  630   a ,  630   b , and  630   c  of multi-card displays  634   a  and  634   b , thus removing the top row of cards; e.g., cards  630   a ,  630   b , and  630   c , from view on multi-card displays  634   a  and  634   b.    
     Scenario  620  continues with clutch  642  being released while sub-focus  638  is on card  630   g . Clutch  642  can be released by the wearer removing one or both of their fingers from the touch-based UI of the HMD. After clutch  642  is released, the HMD can use a single-user view to display either (a) card  630   c , as the card being focused on before clutch operation  642  began, or (b) card  630   g , as the card focused on using sub-focus  638  just prior to release of clutch  642 . In response to clutch  642  being released for HMD embodiments not using sub-focus  638 , the HMD can use a single-user view to display card  630   c.    
       FIG. 6C  shows a scenario  650  for using clutch operation  680  to generate a multi-timeline display  664   a , according to an example embodiment. Scenario  650  begins with an HMD displaying main timeline  660  with a focus on card  660   a . During scenario  650  prior to clutch  680 , the HMD displays cards in main timeline  660  using a single-card view, displaying a focused-upon card. As the focus is on card  660   a , the HMD displays a single-card view of card  660   a.    
     Scenario  650  continues with a wearer of the HMD performing clutch operation  680 . Upon recognition of clutch operation  680 , in scenario  650 , the HMD can generate and display multi-timeline display  664   a , which is shown in an expanded view as multi-timeline display  664   b . In some embodiments, the HMD can focus on the entire multi-timeline display  664   a  using focus  666 . In other embodiments, the HMD can focus a subset of cards and/or timelines, such as, but not limited to, a single card, one, some, or all cards on a timeline, a column of cards across one or more timelines, a block of cards across multiple timelines, a single timeline, a group of timelines, or some other selection of cards and/or timelines, within multi-card display  664   a  using sub-focus  668 . 
     As shown in  FIG. 6C  using expanded multi-timeline display  664   b , the multi-timeline displays five timelines (TLs): timelines  670 ,  672 ,  674 ,  676 , and  678 . The multi-timeline display displays five cards for each of displayed timelines  670 ,  672 ,  674 ,  676 , and  678 . The timelines can be selected for display based on a type of object displayed in a card; e.g., a timeline having only photos, only photo bundles, only messages, only message bundles, only cards representing active applications. Additional criteria can be used to further select items for a timeline; e.g., for photo objects, some criteria can be: only photos taken before (or after) a predetermined date, within a date range, at a location, as part of a photo bundle, photos that were shared, photos that were shared and with one or more messages received in response, etc. Other criteria for photo objects and/or other types of objects are possible as well for selection in a timeline. For example, in scenario  650 , all of the cards in timeline  670  represent photos in a photo bundle, all of the cards in timeline  672  represent photos taken in a given city location, and all of the cards in timeline  678  represent contacts that do not have associated photos/images. 
     The additional timelines presented can represent different user accounts associated with the HMD, for example, a first timeline could be cards generated by a user&#39;s work account, e.g., photos, events, contacts, email, messages, sent to or received by his/her work account, e.g., user@google.com. In this example, the HMD could be configured to allow access to multiple user accounts, such as the user&#39;s personal account, e.g. user@gmail.com; such that a second timeline accessible from the grid view could be cards generated by the user&#39;s personal account, e.g., photos, events, contacts, email, messages, sent to or received by his/her personal account. This way, the user can easily interact with the HMD via different profiles or personas, such as work or personal. 
     The timelines can be selected to be part or all of the main timeline; for example,  FIG. 6C  shows that timeline  674  includes five cards selected from main timeline  660 . Cards can be selected from main timeline  660  randomly, based on focus  662 , based on a type of object represented on the main timeline; e.g., select only cards representing active applications visible from the main timeline, and/or based on other criteria. For example, in scenario  650 , timeline  674  includes card  660   a , which was the focused-on card prior to clutch  680 , and the two cards on each side of card  660   a  in main timeline  660 . Other criteria for selecting cards from a main timeline are possible as well. 
     One or more timelines can act as contextual menu(s) for multi-timeline display  664   a , including possible operations that can be performed from multi-timeline display  664   a , operations on multi-timeline display  664   a , and/or other operations. For example, timeline  678  includes a menu of operations including navigate, take a video, take a photo, remove a timeline option, and add a timeline. Other operations are possible as well. For example, if clutch is engaged from card  660   a  in main timeline  660 , the multi-timeline display  664   a  could present a contextual menu of operations that could be executed based off of the presently selected card  660   a , e.g. share this card, delete the card, remove from timeline, add to bundle, etc. 
     In one embodiment, the wearer of the HMD can navigate around multi-timeline display  664   a ,  664   b  using head movements. For example, in scenario  650 , the HMD is configured to display sub-focus  668 , shown as a dotted line on both multi-timeline displays  664   a  and  664   b , shown focusing on a single timeline; e.g., timeline  668 . 
     In one example of scenario  650 , “wrap-around” movements, or moving off the end of a row or column to the respective other end of the row or column, are enabled. Then, in response to respective movements upward, downward, leftward, or rightward by the head of the wearer, the sub-focus  668  can move from timeline  674 , as shown in  FIG. 6C , to respective timelines  672 ,  676 ,  672 , or  676 . In particular embodiments, wrap-around can be inhibited, so moving the head of the wearer leftward will not move sub-focus  668  from timeline  674  to timeline  672  and moving the head of the wearer rightward will not move sub-focus  668  from timeline  674  to timeline  676  but rather sub-focus  668  will stay on timeline  674  in response to either the leftward or the rightward movement. 
     In some embodiments, in response to respective movements diagonally up-and-left, up-and-right, down-and-left, and down-and-right by the head of the wearer with wrap-around enabled, the sub-focus  668  can move from timeline  674 , as shown in  FIG. 6C , to respective cards  672 ,  672 ,  676 , and  676 . In particular embodiments, wrap-around can be inhibited, but as each of the diagonal movements has an up or down components, movement to a respective timeline will succeed when sub-focus  668  is on timeline  674 . 
     In some embodiments, sub-focus  668  may not be used. For example, in these embodiments, a leftward head movement can move each of timelines  670 ,  672 ,  674 ,  676 ,  678  to the left on multi-timeline display  664   b  by one or more cards and a rightward head movement can move each of timelines  670 ,  672 ,  674 ,  676 ,  678  to the right on multi-timeline display  664   b  by one or more cards. Also in these embodiments, an upward head movement can bring a time “above” timeline  670  (not shown in  FIG. 6C ) into view as a top-most timeline on multi-timeline displays  664   a  and  664   b , move down each of timelines  670 ,  672 ,  674 ,  676  by one time line on multi-timeline displays  664   a  and  664   b , and remove timeline  678  from view. Further, an upward head movement can bring a time “below” timeline  678  (not shown in  FIG. 6C ) into view as a bottom-most timeline on multi-timeline displays  664   a  and  664   b , move up each of timelines  672 ,  674 ,  676 ,  678  by one timeline on multi-timeline displays  664   a  and  664   b , and remove timeline  670  from view. 
     Other types of head movements and/or UI operations can be used as well or instead with multi-timeline display  664   a ,  664   b , including but not limited to head movements and/or UI operations that move the focus faster than and/or slower than one timeline at a time, enable navigation of cards within a timeline, which can include some or all of the navigation techniques discussed above regarding multi-card displays  634   a  and  634   b , zooming in and out, reshaping sub-focus  668 , selecting card(s)/timeline(s), and deselecting card(s)/timeline(s). 
     Scenario  650  continues with clutch  680  being released while sub-focus  668  is on timeline  670 . After clutch  680  is released, the HMD can use a single-card view to display a card on selected timeline  670 . 
     The user interface can use contextual menus to designate operations for specific objects, applications, and/or cards.  FIG. 7  shows user-interface scenario  700  including contextual menus, according to an example embodiment. A contextual menu is a menu of operations or other possible selections based on a card. In some instances, a contextual menu may be based on the content provided by the card or a content type of the card. For example, if the card includes video content, a contextual menu can include operations such as sharing the video, editing the video, watching the video, deleting the video, adding the video to a “video bundle” or collection of videos, annotating the video, adding, deleting and/or editing sound associated with the video, and/or other operations related to the video, including but not limited more or fewer options. 
     Scenario  700  begins with the HMD receiving a tap while displaying image  710 . In some embodiments, image  710  is part of a timeline. In response to the tap, the HMD can select operations for a contextual menu, such as sharing and deleting the photo, based on the displayed card; e.g., image  710 . To display the contextual menu, the HMD can then display card  720  to indicate that a share operation can be performed on image  710 . Card  720  also shows two dots to indicate that the current contextual menu has two options, with the leftmost dot being black and the rightmost dot being white to indicate that the current Share option is the first option of the two options. 
     To select the other option in the contextual menu, a wearer can perform a swipe operation while card  720  is displayed. In response to the swipe operation, card  722  can be displayed, where card  722  is associated with a delete operation for image. As with card  720 , card  722  shows two dots to indicate that the current contextual menu has two options, with the leftmost dot being white and the rightmost dot being black to indicate that the current Delete option is the second option of the two options. A swipe operation while displaying card  722  causes (re)display of card  720 . 
     If a tap operation is received while displaying card  720 , the HMD can interpret the tap operation as selection of the Share option of the contextual menu. In response, a “people chooser” can be used to select a first person for sharing. 
     The people chooser can display card  730 , which includes an image and a name of a first contact.  FIG. 7  shows that card  730  indicates the first person as “Jane Smith.” In response to viewing card  730 , the wearer can instruct the people chooser to show other possible recipients of photo  710  via swiping through a list of contacts. In scenario  700 , the list of contacts can be represented by cards that include: card  732   a  showing “Another Person,” card  732   b  showing “Friends,” and card  732   c  indicating other person(s), circle(s), and/or social network(s) for sharing photos. People choosers are also discussed in more detail at least in the context of  FIG. 8 . 
       FIG. 7  shows that swiping left while card  732   c  is displayed to request a next possible recipient can lead to re-displaying card  730  associated with Jane Smith. Similarly,  FIG. 7  shows that swiping right while card  730  is displayed to request a previous possible recipient can lead to card  732   c.    
     In scenario  700 , the wearer taps on the touch-based UI while card  730  is displayed, indicating that the wearer wishes to share image  710  with Jane Smith. In response to this tap, card  734  is displayed, which includes the word “Sending” and a progress bar. In scenario  700 , the HMD is configured to wait for a “grace period,” such as one or a few second(s), before carrying sending or deleting images, to give the wearer a brief interval to cancel sending or deleting the image. 
     The progress bar on card  734  can show the passing of the time of the grace period for sending image  710 . Once the grace period expires or a tap is received, the HMD can send image  710 , e.g., via e-mail or multi-media message, to Jane Smith. If image  710  is sent successfully, the HMD can display card  736  with text of “Sent” to indicate that image  710  was indeed successfully sent to Jane Smith. After displaying card  736 , the HMD can return to a timeline display, such as discussed above in the context of at least  FIG. 5A . 
     If image  710  is not sent successfully or was cancelled, such as by the wearer performing a swipe down operation during the grace period, the HMD can display card  738  to indicate to the wearer that the HMD was unsuccessful in sending image  710  sent to Jane Smith. After displaying card  738 , the HMD can return to a timeline display, such as discussed above in the context of at least  FIG. 5A . 
     If a tap operation is received while displaying card  722 , which  FIG. 7  shows is the “Delete” card, the HMD can interpret the tap operation as selection of the Delete option of the contextual menu. In response to this tap, the HMD can display card  740  with text of “Deleting” and a progress bar for a grace period that has to expire before the HMD will delete image  710 . Once the grace period expires or a tap is received, the HMD can delete image  710 . Once image  710  is deleted, the HMD can display card  742  to indicate to the wearer that image  710  was indeed deleted. After displaying card  742 , the HMD can return to a timeline display, such as discussed above in the context of at least  FIG. 5A . 
       FIG. 7  also shows that at any time while displaying cards  720 ,  722 ,  730 ,  732   a - 732   c ,  734 ,  736 ,  740 , and  742 , a swipe down operation can be performed. In response, the HMD can stop the current operation; e.g., send or delete, and return to displaying image  710 . 
     The UI can utilize “people choosers” or software configured to help a wearer find a person from among the wearer&#39;s contacts, such as when the wearer wants to contact that the person.  FIG. 8  shows a user-interface scenario  800  including a people chooser, according to an example embodiment. In scenario  800 , two techniques are shown for invoking the people chooser. While card  810  is displayed, a wearer of an HMD can use a voice interface that requests that the wearer “Speak a name from your contacts.” Also or instead, at  812 , the HMD can be in a contextual menu with a “Share” option that is selected. 
     After either card  810  or  812  is displayed, the people chooser is invoked to permit selection of a person or “contact” as a destination for sharing, being called, looked up in a contact directory, or some other activity. The people chooser sorts contacts by frequency of use, rather than by time of use; e.g., recently chosen contacts, to be a useful alternative to the timeline. 
       FIG. 8  shows that card  820  is selected for display by the people chooser. Card  820  represents “Jane Smith.” In scenario  800 , Jane Smith is the most frequently used contact. Card  820  includes the contact&#39;s name, Jane Smith, and an image related to the contact, e.g., a picture of Jane Smith. After reviewing the card shown at  820 , the wearer of the HMD can either tap or swipe the touch-based UI to select “Jane Smith” as the person selected for the activity; e.g., sharing, calling, etc., that can lead to invocation of the people chooser. 
     If a tap is received while card  820  is shown, the HMD can then take action  822  with the choice. If a swipe is received while card  820  is displayed, then another card can be displayed for a next-most recent contact; e.g., card  824  for “Another Person.” To select “Another Person” for the action while card  824  is displayed, a wearer can either tap the HMD using the touch-based UI or say the person&#39;s name, e.g., “Another Person,” using the voice-based interface. If “Another Person” is selected, the HMD can carry out the action with “Another Person.” 
     Otherwise, “Another Person” is not selected. Then, the wearer can swipe again, and another card can be displayed for a group of contacts, such as card  826  for “Friends.” To select a “Friend” for the action while card  826  is displayed, a wearer can either tap the HMD using the touch-based UI or say the person&#39;s name, e.g., “Friend,” using the voice-based interface. If the “Friends” group is selected, the HMD can provide cards in the “Friends” group in response to swipe actions until either a contact in the “Friends” group is selected or the “Friends” group is exhausted without the wearer making a selection. Each item in the “Friends” group, or friend, can be a contact or other representation of a person, organization, group, family, etc. that the wearer has designated as a friend. In one embodiment, the “Friends” group can be a bundle or folder that enables access to the items or friends within the bundle or folder. In one embodiment, the “Friends” group can be a group of friends ordered based on time of friend designation, most recent access, or by some other criteria. 
     Otherwise, “Friends” are not selected. Then, the wearer can swipe while card  826  is displayed to bring up card  828 , representing another contact frequently called by the wearer. Scenario  800  can continue with swipes that show contacts until either a contact is selected or until all contacts have been displayed. If all contacts have been displayed, after displaying the last selected contact, the HMD can “wrap-around” or return to the first selected card; e.g., card  820  representing “Jane Smith.” 
     As mentioned above, the HMD can be configured with a camera, and the UI can aid wearer interaction with the camera.  FIG. 9  shows a user-interface scenario  900  with camera interactions, according to an example embodiment. Scenario  900  can begin by displaying card  910  or card  930  for an HMD configured with one or more cameras that can perform at least the activities described herein. 
     While displaying card  910 , at any point while utilizing the UI of the HMD, the camera button; e.g., button  179  of HMD  172  shown in  FIG. 1D , can be pressed for either a short time; e.g., less than one second, or a long time; e.g., longer than the short time. If the camera button is pressed for the short time, also referred to as a “short press” of the camera button, scenario  900  continues by displaying card  920 . Otherwise, if the camera button is pressed for the long time, also referred to as a “long press” of the camera button, scenario  900  continues by displaying card  934 . 
     In response to the short press of the camera button, a photo or still image is captured using the camera—an example image capture is shown as card  920 . If, after capturing the photo, a tap is received, scenario  900  continues by displaying card  922 ; otherwise, if either a swipe down is received or no interaction with the touch-based UI is recorded during a wait interval; e.g., one second, scenario  900  continues by displaying card  924 . 
     Card  922  is part of a contextual menu with options for operating on the captured photo. The contextual menu can include options such as a share option for the captured photo; e.g., as indicated by the “Share” card shown at  922 , a delete option for the captured photo, and other options for the captured photo (e.g., editing the photo). 
     Card  924  shows the captured photo as “animated out”; that is, the image of the captured photo is replaced with a blank card shown as card  926  via an animated transition. After displaying card  926 , the HMD can return to a previous state; e.g., a position in the timeline being displayed at  910  before receiving the short press of the camera button. 
     After displaying a home card, such as card  300  shown in  FIG. 3 , a tap can be received via the touch-based UI. In response to the tap, the HMD can display a “Capture” card, such as card  930 . After displaying card  930 , scenario  900  can continue with a display of card  932 . 
     Card  932  is shown in  FIG. 9  as a “Photo” card, indicating that to the wearer that a photo or still image can be captured using the camera. If a swipe is received while displaying card  932 , scenario  900  can continue by displaying card  934 ; otherwise, scenario  900  can continue at  950 . 
     Card  934  is shown in  FIG. 9  as a “Video” card to indicate to the wearer that a video can be captured using the camera. If a swipe is received while displaying card  934 , scenario  900  can continue by displaying card  936 . In one embodiment, multiple camera operations can occur simultaneously; e.g., the HMD can perform some or all of recording video, capturing still images, capturing timelapse images, and conducting video conferencing at the same time. In more particular embodiments, the HMD can perform the multiple camera operations and/or multiple telephone operations simultaneously; e.g., the HMD can, while perform multiple camera operations, conduct one or more two-party or multi-party voice calls, dial one or more parties, have one or more voice calls on hold, forward one or more voice call, and other telephone operations. 
     Otherwise, the HMD can determine whether a new video session is to be started to capture the requested video or if a pending video session is to be rejoined. If the new video session is to be started, the HMD can trigger the camera to start recording images (if not already recording) and scenario  900  can continue by displaying card  950 . If the pending video session is to be rejoined, the HMD can redirect to, or request display of, an already-existing card for the pending video session and scenario  900  can continue by displaying a card for the pending video session, shown in  FIG. 9  as card  952 . 
     Card  936  is shown in  FIG. 9  as a “Timelapse” card to indicate to the wearer that a timelapse image can be captured using the camera. If, a swipe is received while displaying card  936 , scenario  900  can continue by displaying card  932 . 
     Otherwise, the HMD can determine whether a new timelapse session is to be started to capture the requested timelapse image or if a pending timelapse session is to be rejoined. If the new timelapse session is to be started, the HMD can trigger a timelapse card to start displaying a timelapse image being captured by the camera (if not already recording) and scenario  900  can continue by displaying card  960 . If the pending timelapse session is to be rejoined, the HMD can redirect to an already-existing card for the pending timelapse session and scenario  900  can continue by displaying a card for the pending timelapse session, shown in  FIG. 9  as card  962 . 
     Upon displaying card  940 , the HMD can launch a temporary view finder and instruct the camera to begin capturing images. Upon capturing each image, the HMD can display the image. While displaying the image, the wearer can either (a) provide a tap to the HMD and scenario  900  can continue by displaying card  942  or (b) provide a swipe down using the HMD and scenario  900  can continue by displaying card  944 . 
     Upon displaying card  942 , the HMD can capture an image using the camera. Once captured, the HMD can display the captured image for a short period of time; e.g., one or a few seconds. After displaying the captured image for the short period, scenario  900  can proceed to display card  940 . 
     Upon displaying card  944 , which is a blank card, any image for possible capture, e.g., card  940 , animates out. In some embodiments, the camera can be deactivated after animating out the image, if no other application; e.g., video, is using the camera. After displaying card  944 , the HMD can return to a previous state; e.g., a position in the timeline being displayed at  910  before reaching  944 . 
     Card  950  can be a card representing the new video session. While the video session is active, the HMD can capture images and, in some embodiments, sound, and store the captured video. Upon capturing each image for the video session, the HMD can display the captured image using card  950 , which represents the new video session. While displaying the images for the video session using card  950 , the wearer can either (a) provide a tap to the HMD and scenario  900  can continue by displaying card  954  or (b) provide a swipe down using the HMD and scenario  900  can continue by displaying card  956 . 
     Card  952  can be a card representing the pending video session. While the video session is active, the HMD can capture images, and in some embodiments, sound, and store the captured video. Upon capturing each image for the video session, the HMD can display the captured image using the card  952 , which represents the pending video session. While displaying the images for the video session using card  952 , the wearer can either (a) provide a tap to the HMD and scenario  900  can continue by displaying card  954  or (b) provide a swipe down using the HMD and scenario  900  can continue by displaying card  956 . 
     Card  954  can represent a contextual menu with options for the captured video. The contextual menu can include options for the captured video, such as a stop recording option, restart recording option, delete video option, and other options. 
     Card  956  can be a blank card indicating to the wearer that the video session has terminated. In some embodiments, the captured video can be deleted after the video session is stopped, while in other embodiments, the captured video or audio video can remain in storage after the video session is stopped. In some embodiments, the camera can be deactivated if no other application; e.g., a timelapse photo capture, is using the camera. In other embodiments, after displaying the blank card, the HMD can return to a previous state; e.g., a position in the timeline being displayed using card  910  before card  956  was ever displayed. 
     Card  960  can represent the new timelapse session. While the new timelapse session is active, the HMD can capture images for addition to the timelapse image. Upon capturing each image for the timelapse session, the HMD can display image(s) related to the new timelapse session using card  960 . While displaying card  960 , the wearer can either (a) provide a tap to the HMD and scenario  900  can continue by displaying card  964  or (b) provide a swipe down using the HMD and scenario  900  can continue by displaying card  966 . 
     Card  962  can represent the pending timelapse session. While the pending timelapse session is active, the HMD can capture images for addition to the timelapse image. Upon capturing each image for the timelapse session, the HMD can display image(s) related to the pending timelapse session using card  962 . While displaying card  962 , the wearer can either (a) provide a tap to the HMD and scenario  900  can continue by displaying card  964  or (b) provide a swipe down using the HMD and scenario  900  can continue by displaying card  966 . 
     Card  964  can represent a contextual menu with options for the captured timelapse image. The contextual menu can include options for the captured timelapse image, such as a stop timelapse option, a timelapse frequency option, a restart timelapse option, and other options. 
     Card  966  can be a blank card that indicates to the wearer that the timelapse session has terminated. In some embodiments, the captured timelapse image can be deleted after the timelapse session is stopped, while in other embodiments, the captured timelapse image can remain in storage after the timelapse session is stopped. In some embodiments, the camera can be deactivated if no other application; e.g., video is using the camera. In other embodiments, after displaying the blank card, the HMD can return to a previous state; e.g., a position in the timeline being displayed using card  910  before card  966  was ever displayed. 
     Objects, such as photos and messages, can be grouped or bundled by the UI to simplify interactions with these bundles.  FIG. 10A  shows user-interface scenario  1000  with photo bundles, according to an example embodiment. Scenario  1000  begins with an HMD displaying photo bundle card (PBC)  1010  in a timeline. Photo bundle card  1010  includes photo bundle indicator (PBI)  1010   a , example photo  1010   b , and thumbnails  1010   c . Photo bundle indicator  1010   a , shown in  FIG. 10A  as a page with a turned-down corner, indicates that a “photo bundle” or collection of photos is associated with photo bundle card  1010 . Example photo  1010   b , shown in  FIG. 10A  as occupying roughly one-half of photo bundle card  1010 , provides a relatively large image of an example photo in the photo bundle. Thumbnails  1010   c , shown in  FIG. 10A  as collectively occupying roughly one-half of photo bundle card  1010 , provides four relatively small images of four example photos in the photo bundle. 
     While displaying photo bundle card  1010 , the wearer of the HMD can tap on a touch-based UI to instruct the HMD to display the photos in the photo bundle. During scenario  1000 , while displaying photo bundle card  1010 , the HMD can receive a tap and subsequently display a card with photo  1012 . 
     Each individual item within a bundle, e.g., a photo within a photo bundle, functions the same with respect to the user interface as it would if the item were displayed on the timeline. For example, in the case of a photo, such as photo  1012 , tapping on the touch-based UI would enter a contextual menu for the photo, and swiping down while in the contextual menu would return to photo  1012 . 
     While displaying photo  1012 , the HMD can receive a swipe forward to display the next photo in the bundle or a swipe backward to display the previous photo in the bundle. In scenario  1000  as shown in  FIG. 10A , the next photo can be photo  1014 . As photo  1012  is the first photo in the bundle, the previous photo is the last photo in the bundle, or photo  1018 . 
     During scenario  1000 , the HMD receives a swipe backward while displaying photo  1012 . In response to the swipe backward, the HMD can display photo  1018  as discussed above. Scenario  1000  continues with the HMD receiving two more swipes backwards. In response, the HMD can first display photo  1016  which is the previous photo to photo  1018 , and, after receiving the second swipe backward, display photo  1014  which is the previous photo to photo  1016  as shown in  FIG. 10A . 
     While displaying photo  1014 , the HMD can receive a tap. In response to the tap, the HMD can display photo bundle card  1010  and scenario  1000  can end. 
       FIG. 10B  shows user-interface scenario  1050  with message bundles, according to an example embodiment. Scenario  1050  begins with an HMD displaying message bundle card (MBC)  1060  in a timeline. Message bundle card  1060  includes message bundle indicator (MBI)  1060   a  and a most-recent message in the message bundle, which includes image  1060   b  and message  1060   c . Message bundle indicator  1060   a , shown in  FIG. 10B  as a page with a turned-down corner, indicates that a “message bundle” or collection of messages is associated with message bundle card  1060 . Image  1060   b  can be an image associated with the sender of the most-recent message in the message bundle. Message  1060   c  can include text, and in some embodiments, other type(s) of data, that is sent with the most-recent message in the message bundle. As shown in  FIG. 10B , image  1060   b  occupies roughly one-third of message bundle card  1060 , is an image of “Joe W.” who sent message  1060   c , which occupies roughly two-thirds of message bundle card  1060 . Message  1060   c  includes text that says “Sounds great. See you there,” and was sent three minutes ago. 
     In scenario  1050 , while displaying message bundle card  1060 , the wearer of the HMD can tap on a touch-based UI. Some bundles have additional functionality, specific to the bundle, associated with a tap. In the example of the message bundle, a contextual menu can be displayed in response to the tap.  FIG. 10B  shows two options in the contextual menu: a reply option associated with card  1070  and a read-all option associated with card  1072 . 
     While card  1070  associated with the reply option is displayed, the HMD can receive a tap. In response, the HMD can interpret the tap as a selection to reply to the most recently displayed message card. While card  1072  associated with the read all option is displayed, the HMD can receive a tap, which can be interpreted to read the messages in the message bundle, starting with the most recent. In one embodiment, the HMD can start with the first message in the message bundle rather than the most recent. In response to receiving a swipe down while in the contextual menu for message bundles, the HMD can select message bundle card  1060  for display. 
     Each individual item within a bundle, e.g., a message within a message bundle, functions the same with respect to the user interface as it would if the item were displayed on the timeline. For example, in the case of a message, such as message  1062 , tapping on the touch-based UI would enter a contextual menu for the message, and swiping down while in the contextual menu for the message would return to message  1062 . 
     While displaying message  1062 , the HMD can receive a swipe forward to display the next message in the bundle or a swipe backward to display the previous message in the bundle. In scenario  1050  as shown in  FIG. 10B , the previous message can be message  1064 . As message  1062  is the first message in the bundle, there is no “next” message, so the last message in the bundle, or message  1066 , can be displayed instead. 
     During scenario  1050 , the HMD receives a swipe forward while displaying message  1062 . In response to the swipe forward, the HMD can display message  1066  as discussed above. Scenario  1050  continues with the HMD receiving two more swipe forwards. In response, the HMD can first display message  1064  which is the next message to message  1066 , and, after receiving the second swipe forward, display message  1062 , which is the next message to message  1064  as shown in  FIG. 10B . 
     While displaying message  1062 , the HMD can receive a tap. In response to the tap, the HMD can enter a contextual menu for message  1062  and scenario  1050  can end. 
     E. Grouping of Cards by Time Periods and Content Types 
     Cards may be grouped by timeline grouping methods and algorithms. For illustration, consider a timeline grouping algorithm for a chess game application. In practice, a chess game may involve various moves made by a player and an opponent. In some instances, the player may be playing two separate games simultaneously against two different opponents. As such, a timeline of moves may illustrate the player&#39;s moves made against the first opponent and the player&#39;s moves made against the second opponent. Further, the timeline may group the player&#39;s moves made against the first opponent separately from the player&#39;s moves made against the second opponent. In addition, the player&#39;s moves made against the first opponent (e.g., three different moves) may be combined into one bundle card on the timeline. Further, the player&#39;s moves made against the second opponent (e.g., five different moves) may be combined into a separate bundle card on the timeline. 
     In addition, a timeline can include various types of content. For example, the timeline of moves described above may be expanded to also include cards representing past games played (e.g., the player versus previous opponents), different types of games played (e.g., checkers, backgammon, and cards), and even actions associated with the player (e.g., activities before each game). In some instances, the timeline may include cards related to the player&#39;s activities throughout a given time period. For example, a card may be added to the timeline for each activity the player is involved in throughout the day. 
     Cards associated with a timeline may be grouped by time.  FIG. 11A  shows a scenario with cards grouped on a timeline, according to an example embodiment. In particular, scenario  1100  illustrates timeline  1102  with cards provided side-by-side, possibly through an electronic display, such as an HMD. In some instances, an order for a plurality of cards may be determined. In particular, cards  1102   a - 1102   h  can be arranged in timeline  1102  with each card time-stamped such that each card is associated with a specific time. For example, cards  1102   a - 1102   h  may be chronologically ordered from left to right based on specific time-stamps for each card. In particular, the cards may be ordered based on the times when each card was added to timeline  1102 . As such, card  1102   a  may have been created before any of cards  1102   b - 1102   h , card  1102   b  may have been created after card  1102   a  and before card  1102   c , card  1102   c  may have been created after card  1102   b  and before card  1102   d , and so on. 
     In some embodiments, cards associated with the timeline may be grouped by a time period. In some instances, cards on a timeline may be grouped by multiple time periods. For example, cards on a timeline may be grouped by a past time period, a present/on-going time period possibly including the current time, and a future time period. As such,  FIG. 11A  illustrates timeline  1102  with cards  1102   a - 1102   h  grouped by a past time period  1102 I, a present/on-going time period  1102 J, and a future time period  1102 K. In some embodiments, groups of cards may be referred to as “decks” of cards. For example, the groups of cards associated with timeline  1102  may also be referred to as past deck  1102 I, present/on-going deck  1102 J, and future deck  1102 K. 
     As such, cards  1102   a - 1102   c  may be associated with past time period  1102 I and may be referred to as being grouped in past deck  1102 I. Further, cards  1102   d  and  1102   e  may be associated with present/on-going time period  1102 J and may be referred to as being grouped in present/on-going deck  1102 J. Yet further, cards  1102   f - 1102   h  may be associated with future time period  1102 K and may be referred to as being grouped in future deck  1102 K. In addition, card  1102   d  may be a home card illustrating the present time of 3:28. Card  1102   a  may represent a previous photo taken, perhaps captured during a specific time of 1:28, which 2 hours prior to the present time of 3:28 illustrated on card  1102   d . Further, card  1102   h  may represent a scheduled flight that the user may be scheduled to board tomorrow at 7:09 p.m. 
     It should be noted that cards from one time period may move to another time period. In some instances, cards from present/on-going deck  1102 J may move to either past deck  1102 I or future deck  1102 K. For example, cards from present/on-going deck  1102 J may move to past deck  1102 I after each day (e.g., 24 hours after the time each card is added to timeline  1102 ). Further, cards from present/on-going deck  1102 J that are associated with a future time may move to future deck  1102 K immediately after being viewed on timeline  1102  (e.g., after being shown on a display). For example, card  1102   h  may be in present/on-going deck  1102 J when initially added to timeline  1102 , providing flight information for “Flight VA 29” at “7:09 p.m.” Since the calendar entry is associated with a future time (e.g., tomorrow at 7:09 p.m.), card  1102   h  may be moved from present/on-going deck  1102 J to future deck  1102 K immediately after being shown on timeline  1102 . Yet further, cards from present/on-going deck  1102 J may move to either past deck  1102 I or future deck  1102 K due to additional cards being added to timeline  1102 , possibly due to cards crowding the view on a display. In addition, cards may move to either past deck  1102 I or future deck  1102 K due to the passage of time. 
     In some embodiments, a card may be associated with a content type. For example, an application of a card may be associated with at least one content type. As shown, timeline  1104  illustrates various content types provided by cards  1102   a - 1102   h  or by an application associated with the cards. In particular, timeline  1102  illustrates the following content types: an image content type for card  1102   a , possibly captured by a camera associated with the HMD, a message content type for card  1102   b , possibly received by an electronic messaging application of the HMD, and a phone call content type for card  1102   c , possibly generated by a phone call application of the HMD. 
     In addition, other content types may include: a time content type for card  1102   d , possibly providing the present time, and a camera content type for card  1102   e , possibly capturing an image relative to the present time. Further, additional content types may include: a weather content type for card  1102   f , possibly representing weather forecast information at a time two hours from the present time, an event content type for card  1102   g , possibly representing a scheduled event for “Lunch with Monica Kim” in two hours, and as noted, a flight content type for card  1102   h.    
     It should be noted that cards  1102   a - 1102   h  may have the similar content types as other cards described above (e.g., cards illustrated in  FIGS. 5A, 5B, and 7 ) but may also have different content types as well. For example, there may be a content type for “settings” such that the HMD may be calibrated or initialized with appropriate configurations suitable for a wearer of the HMD. Yet further, sub-content types may be described herein. For example, “location” may include sub-content types for navigation, GPS tracking, and saved locations such as home, school, work, and/or landmarks such as the Golden Gate Bridge. Yet further, “events” may include sub-content types for activities/occasions such as sporting events, live hangout sessions, calendar events, and holidays, among other possibilities. Still further, “video” may include interactive video conferencing, video streaming including voice recordings and voice activation, and video uploads. Many other content types and sub-content types are possible as well. 
     To illustrate the grouping of cards by content type, cards may be represented by an associated content type. For example, timeline  1104  illustrates that each card of cards  1102   a - 1102   h  on timeline  1102  may relate to at least one content type. As such, past deck  1104 A illustrates that the content of card  1102   a  includes an “Image (I),” the content of card  1102   b  includes a “Message (M),” and the content of card  1102   c  includes a “Phone call (P).” Further, present/on-going deck  1104 B illustrates that the content of card  1102   d  includes a “Time (T)” and the content of card  1102   e  includes “Camera (C)” information. Yet further, future deck  1104 C illustrates that the content of card  1102   f  includes “Weather (W)” information, the content of card  1102 g includes “Event (E)” information, and the content of card  1102   h  includes “Flight (F)” information. 
     Further, to illustrate the grouping of cards by content type, cards may be represented by letters or symbols designating content types. For example, timeline  1106  illustrates the types of content identified from timeline  1104 . In particular, timeline  1106  represents different content types using letters. For instance, timeline  1106  illustrates “I M P” in past deck  1106 A to represent the cards in past deck  1104 A with the content types of an “Image (I),” a “Message (M),” and a “Phone call (P).” Further, the “T C” in present/on-going deck  1106 B represents the cards in present/on-going deck  1104 B with the content types of “Time (T)” and “Camera (C)” information. Yet further, the “W E F” letters in future deck  1106 C represent the cards of future deck  1104 C with the content types of a “Weather (W),” “Event (E),” and “Flight (F)” information. 
     In some embodiments, cards in a group may be bundled or combined to determine a time-stamped bundle card. A time-stamped bundled card may also be referred to as a bundle card for simplicity.  FIG. 11B  shows scenario  1110  of bundling cards, according to an example embodiment. In particular, scenario  1110  illustrates a timeline  1112  representing cards with various types of content that may be provided by an HMD. Similar to timeline  1106  of  FIG. 11A , timeline  1112  illustrates letters for representing cards by content type. For example, past deck  1112 A includes one “I” representing one card with an image content type, one “M” representing one card each with a message content type, one “P” representing one card with the a phone call content type. In some instances, the image card, message card, and the phone call card of past deck  1112 A may be combined into a bundle card on timeline  1112 , possibly representing cards in past deck  1112 A. 
     In some instances, cards may not be combined into a bundle card. For example, present/on-going deck  1112 B includes cards T, C, and W, representing three cards with different content types of time, camera, and weather information, respectively. Since there is only one card for each content type, combining these cards may not be necessary. Further, future deck  1112 C includes W, E, and F, representing three cards with content types of weather information, an event, and a flight. Since there is only one card for each content type, combining these cards may also not be necessary. However, it should be noted that the cards in future deck  1112 C may be combined into a bundle card on timeline  112  to represent cards of future deck  1112 A. 
     In some embodiments, cards may be grouped by time periods and/or corresponding decks of cards. Cards may also be placed into sub-groups possibly referred to as “stacks” of cards. For example, timeline  1114  is another timeline with additional cards represented. In particular, past deck  1114 A may be organized with sub-groups or stacks of cards associated with periods of time represented by a “1 Year Ago” stack, a “1 Month Ago” stack, a “1 Week Ago” stack, and a “1 Day Ago” stack. Further, future deck  1114 C may be organized with sub-groups associated with periods of time, such as an “In 1 Hour” stack, an “In 2 Hours” stack, a “Tomorrow” stack, and in “In 2 Days” stack. Although not illustrated in  FIG. 11B  for simplicity, the present/on-going deck  1114 B may also include stacks such as a “Present Time” stack, a “Five Minutes Ago” stack, and/or an “In 5 Minutes” stack, among other possibilities. 
     In some embodiments, cards may be grouped by time periods and by content type. For example, the cards represented in past deck  1114 A are grouped into the “1 Year Ago” stack, the “1 Month Ago” stack, the “1 Week Ago” stack, and the “1 Day Ago” stack, and further by content types represented by the letters of I, M, and P. Further, the cards represented in the future deck  1114 C are grouped by the “In 1 Hour” stack, the “In 2 Hours” stack, the “Tomorrow” stack, and the “In 2 Days” stack, and are further grouped by content types represented by the letters W, E, and F. 
     It should be noted that the cards represented in the “1 Day Ago” stack of past deck  1114 A may correspond to the same cards as shown in past deck  1112 A. Further, the cards represented in present/on-going deck  1114 B may correspond to the same cards as shown in present/on-going deck  1112 B. Yet further, the cards represented in the “In 1 Hour” stack of future deck  1114 C may illustrate the same cards as shown in future deck  1112 C. As such, timeline  1112  may illustrate cards of timeline  1114  that may be displayed on an HMD at a given time. 
     In some embodiments, cards grouped by time periods may further be combined or bundled by content type. In some instances, cards grouped by time periods may be bundled to determine a bundle card. For example, timeline  1116  of  FIG. 11B  is yet another timeline with a representation of cards. In particular, timeline  1116  illustrates the representation of cards in timeline  1114  such that three or more cards of a given content type are bundled in their respective time periods. As such, bundling of cards may determine, establish, and/or create a corresponding bundle card. As such, timeline  1116  illustrates an example of a bundling threshold number of three cards with a given content type that may be used to bundle the cards for a given time period. It should be noted that a bundling threshold number may simply be referred to as a threshold number, a bundling threshold, and a bundling number, among other possibilities. 
     Considering cards in the “1 Year Ago” stack of past deck  1114 A, there are at least three cards for each of the content types. Thus, these cards may be bundled by the respective I, M, and P content types. As such, each letter, I, M, and P, in the “1 Year Ago” stack of past deck  1116 A appears in boldface letters indicating that at least three cards were bundled for each content type. As such, individual bundle cards replace the three or more cards for each content type. The cards with content types of I and M exceed three-card threshold but the fourth card for these content types may also be bundled in each respective bundle card as well. In other embodiments, the fourth cards for these content types may not be bundled in each respective bundle card and may be displayed separately as non-bundle cards. 
     Further, considering cards in the “1 Month Ago” stack of past deck  1114 A, there are at least three cards for the I and M content types, but not for the P content type. Thus, the cards with I and M content types are bundled by content type. As such, both letters of I and M in the “1 Month Ago” stack of past deck  1116 A appear in boldface letters indicating that at least three cards were bundled to create bundle cards for these content types. Since there are only two cards for the P content type, the two P cards are not bundled and are displayed separately as non-bundle cards. 
     Yet further, there are at least three cards for the I content type in the “1 Week Ago” stack of past deck  1114 A. Thus, only these cards are bundled and the letter I in the “1 Week Ago” stack of past deck  1116 A appears in bold indicating that at least three cards were bundled to create the bundle card for the I content type. Since there is only one card for the M content type and only two cards for the P content type, these cards are displayed separately as non-bundle cards. Additionally, for cards in the “1 Day Ago” stack of past deck  1114 A, there is less than the threshold number of three cards for each content type. Thus, none of the cards are bundled and these cards are displayed separately as non-bundle cards in the “1 Day Ago” stack of past deck  1116 B. Present/on-going deck  1114 B includes letters T, C, and V, and since there are less than three cards for each content type, none of the cards are bundled and these cards are also displayed separately as non-bundle cards in present/on-going deck  1116 B. 
     Further, considering cards of the “In 1 Hour” and “In 2 Hours” stacks of the future deck  1114 C, there are less than three cards for each content type. As the number of cards for each content type is under the threshold number, none of the cards are bundled and these cards are displayed separately as non-bundle cards in respective stacks of future deck  1116 C. For cards in the “Tomorrow” stack of the future deck  1114 C, there are at least three cards for the E content type. Thus, the cards with the E content type in the “Tomorrow” stack of future deck  1116 C are bundled. As such, the letter E appears in bold indicating that at least three cards were bundled to create the bundle card for the E content type. Since there are only two cards for the W content type, the two W cards are not bundled and are displayed separately as non-bundle cards. 
     In addition, for the “In 2 Days” stack of future deck  1114 C, there is at least the threshold number of three cards for both the W and E content types. Thus, the cards for the W and E content types in the “In 2 Days” stack of future deck  1116 C are bundled such that the letters W and E appear in bold. This indicates that at least three cards were bundled to create the bundle cards for the W and E content types. The cards with the E content type exceed the three-card threshold, but the fourth E card may also be bundled as well. In other instances, the fourth E card may not be bundled in its respective bundle card and may be displayed separately along with the non-bundled F card. 
     As mentioned above, cards in the same stack and of a given content type may be bundled if the number of cards meets or exceeds the threshold number. In the examples provided above for timelines  1114  and  1116 , a threshold number of three cards for a given content type may result in bundling the cards. As illustrated in timeline  1114  of  FIG. 11B , a threshold function  1118  may determine the threshold number of cards required for bundling cards. Threshold function  1118  is illustrated as a straight line for requiring the number of cards to meet or exceed a constant number of cards, e.g., three, for bundling the cards. 
     Threshold function  1118  may take other forms as well. For example, threshold function  1118  may take the form of a step function, applying a different threshold value for each stack. For instance, threshold function  1118  may require three cards of the same content type for bundling cards in the “1 Month Ago” stack and only two cards of the same content type for bundling cards in the “1 Year Ago” stack. In another example not shown in  FIG. 11B , threshold function  1118  may require zero cards for present/on-going deck  1114 B, indicating that cards are not bundled for present/on-going deck  1114 B. Further, threshold function  118  may require three cards for each of the “1 Day Ago” and “In 1 Hour” stacks, four cards for each of the “1 Week Ago” and “In 2 Hours” stacks, eight cards for each of the “1 Month Ago” and “Tomorrow” stacks, and sixteen cards for each of the “In 2 Days” and “1 Year Ago” stacks. 
     As noted previously, cards may move from between decks with the passage of time. Further, cards may move from one stack to another stack with the passage of time. For example, cards from present/on-going deck  1114 B may move to the “1 Day Ago” stack of past deck  1114 A twenty-four hours after the cards were added to timeline  1114 . Further, cards from the “1 Day Ago” stack may move to the “1 Week Ago” stack one week after the cards were added to timeline  1114 . Yet further, cards from the “1 Week Ago” stack may move to the “1 Month Ago” stack one month after the cards were added to timeline  1114 , and so on. 
     In some instances, cards may move from present/on-going deck  1114 B to various stacks of future deck  1114 C. In some instances, cards may move from present/on-going deck  1114 B to one of the stacks in future deck  1114 C immediately after the cards are added to timeline  1114 . Yet, in some instances, cards may move to the stacks in future deck  1114 C upon being viewed or focused on by a computing device such as an HMD. In addition, cards may move to the stacks in future deck  1114 C after they are no longer viewable without scrolling through cards on the HMD due to additional cards being added to timeline  1114 . 
     In some embodiments, cards moving from one group to another group may cause a threshold function to adjust the threshold numbers. For example, threshold function  1118  may change threshold numbers as timeline  1114  accumulates more cards. In particular, more cards may be added to the “1 Year Ago” stack and the “In 2 Days” stack. In some instances, the “1 Year Ago” stack may also include cards that were created more than one year ago. Further, the “In 2 Days” stack may include cards that are associated with future times more than two days from the present time. Thus, as the number of cards in the stacks increase, threshold function  1118  may increase or decrease threshold numbers for these stacks. 
     Further, in some instances, threshold function  1118  may change threshold values depending on content type. For example, the “1 Year Ago” stack shown in timeline  1114  may accumulate several image cards but very few message cards. As such, threshold function  118  may maintain the three-card threshold number for image cards but reduce the threshold number for message cards to a two-card threshold number. It should be understood that threshold function  1118  may also be based on an algorithm, an equation, and/or take the form of a function, such as a logarithmic function, for example. Further examples of threshold functions are also described for  FIG. 11D . 
     It should be noted that the grouping methods described herein may bundle cards for various timelines, regardless of the length of the timeline and/or the number of cards on the timeline. In practice, perhaps related to initialization of the timeline, some timelines may contain a couple cards or a few cards. Nonetheless, a threshold function may adjust thresholds according to each timeline and determine threshold numbers based on the number of cards on the timeline. In some instances, the threshold function may have high threshold numbers for timelines with a lower number of cards (e.g., 10-15 cards). However, the threshold function may reduce threshold numbers for timelines with a high number of cards (e.g., 50-100 cards). In addition, the dynamic features of the threshold function may facilitate data storage of the timeline. 
     Data may be stored in accordance with a timeline.  FIG. 11C  illustrates data capacity of a timeline, according to an example embodiment. In some embodiments, data capacities may be illustrated for each time period. As demonstrated in  FIG. 11C , data capacities for each time period may vary in size. For example, the data capacity illustrated for present/on-going time  1122 , yesterday/tomorrow  1124 , and last week/next week  1126  appear nominal compared to the data capacity for last month/next month  1128 . 
     In some embodiments, the data capacity and/or usage associated with each time period may vary according to the length of each time period. For example, the bars illustrated in  FIG. 11C  may represent the data capacity for storing cards in each time period. In some instances, data capacity associated with a timeline may substantially increase as illustrated from present/on-going deck  1122  to yesterday/tomorrow deck  1124 . Additional increases in data capacity may be illustrated by comparing the data associated with yesterday/tomorrow deck  1124  to last week/next week deck  1126 . Yet further, a greater increase in data capacity as time increases may be demonstrated by comparing the data associated with last week/next week deck  1126  to last month/next month deck  1128 . In some instances, such increases in data may be attributed to the number of cards that may be associated with each time period. 
     In some embodiments, data storage capacity for each time period may vary according to the size of each time period. For example, the bars illustrated in  FIG. 11C  may represent the storage capacity of data for each time period. As such, present/on-going card deck  1122  may have the smallest storage capacity for data, followed by the yesterday/tomorrow deck  1124 . Further, the last week/next week deck  1126  may have the next largest storage capacity for data, followed by largest storage capacity for last month/next month deck  1128 . 
     In some instances, when the data storage of present/on-going deck  1122  reaches its maximum data capacity, cards associated with present/on-going deck  1122  may be moved to yesterday/tomorrow deck  1124 . Further, when the data storage of yesterday/tomorrow deck  1124  reaches its maximum data capacity, cards associated with yesterday/tomorrow deck  1124  may be moved to last week/next week deck  1126 . Similarly, cards associated with last week/next week deck  1126  may be moved to last month/next month  1128 . Therefore, last month/next month  1128  may have the largest storage capacity due the additions of cards over time. 
     In some instances, storage capacities may vary in accordance with individual cards moving between card decks or stacks. As noted, cards in present/on-going deck  1122  may be moved to in yesterday/tomorrow deck  1124  on a daily basis (e.g., twenty-four hours after the time a card is added to a timeline). Further, cards from yesterday/tomorrow deck  1124  may be moved to last week/next week deck  1126  also on a weekly basis. Yet further, cards from last week/next week deck  1126  may be moved to last month/next month deck  1128  on a monthly basis. As indicated, numerous cards may be accumulated in the last month/next month deck  1128 , utilizing a larger data capacity than the other card decks. Therefore, storage capacities in accordance with the time periods may change (e.g., storage may be allocated and/or reallocated) to store cards moving between and into individual card decks. 
     It should be noted that some cards (e.g., the data of present/on-going deck  1122  and yesterday/tomorrow deck  1124 ) may be stored in non-transitory computer-readable media (e.g., register memory, processor cache, and/or random access memory (RAM)). Further, the computer readable media may also include non-volatile non-transitory computer readable media. For example, flash memory, writable read-only memory (ROM), and/or magnetic media may be used to store some cards (e.g., data of last week/next week deck  1126  and last month/next month deck  1128 ). In some instances, all data associated with the card decks may be stored using on-board data storage (e.g., memory  218  from  FIG. 2A ) and the on-board data storage may be allocated according to varying storage capacities due to cards moving between card decks and/or stacks. In other instances, some or all cards can be stored using off-board storage devices not resident on the HMD. Other possibilities may also exist. 
     In some embodiments, the number of cards grouped for a given time period may depend on or vary with the duration between the present/on-going time period and the given period. In some instances, the frequency of grouping cards into bundle cards may vary with the duration between the present time and the first time period. In particular, the number of cards grouped may increase proportionally with an increase in the duration between present time and the given time period.  FIG. 11D  shows a scenario with cards grouped on a timeline and the timeline as provided by an HMD, according to an example embodiment. In particular, scenario  1130  illustrates timeline  1132  with past deck  1132 B, present/on-going deck  1132 C, and future deck  1132 D. 
     As illustrated, time periods that are a longer duration away from present/on-going time period  1132 C may have more cards than time periods closer to present/on-going time period  1132 C. For example, the “&gt;1 Year Ago” time period is the longest duration away from present/on-going time period  1132 C. As such, the “&gt;1 Year Ago” stack includes more cards than any other stack illustrated in  FIG. 11D . Further, the “1 Month Ago” stack is the second farthest away from the present/on-going time period  1132 C and the “1 Month Ago” stack has more cards than the “1 Week Ago” stack or the “1 Day Ago” stack. 
     Further, time periods in future time  1132 D that are longer durations away from present/on-going time period  1132 C may also have more cards than time periods that are closer to present/on-going time period  1132 C. For example, the “&gt;1 Week” time period is the longest duration away from present/on-going time period  1132 C than the other time periods of future time period  1132 D. As such, the “&gt;1 Week” stack includes more cards than any other stack illustrated in future stack  1132 D. Further, a decrease in the number of cards for each stack is illustrated when moving from the “&gt;1 Week” stack to the “In 1-2 Hrs” stack. 
     In some embodiments, the number of cards bundled in a given time period may increase proportionally based on the duration between the present/on-going time period and the given time period. For example, considering the past time period  1132 B, the number of cards bundled in the “&gt;1 Year Ago” stack will be greater than the other stacks of the past time period  1132 . Alternatively, the number of cards bundled for the “&gt;1 Week” stack will be greater than the other stacks in the future time period  1132 D. In some instances, threshold function  1136  and/or  1118  may determine the threshold numbers for the number of cards required to combine cards. 
     In some instances, different threshold numbers may be applied to cards in time periods a given duration away from the present/on-going time period. In some instances, threshold numbers may be based on these durations between the present/on-going time period and other time periods. For example, threshold function  1136  may apply a different threshold number for the “&gt;1 Year Ago” stack (e.g., a two-card threshold number) than the “1 Month Ago” stack (e.g., a three-card threshold number), for example. In other examples, threshold function  1136  and/or  1118  can be expressed by an equation. For instance, threshold function  1136  and/or  1118  may be expressed by one or more of the following expressions: 
         T (stack)= k 1(stack)*diff(stack), 
         T (stack)= k 2(stack)* N (stack), and 
         T (stack)= k 3(stack)*( N (stack)/diff(stack)). 
     The variables above may be defined by the following expressions: 
       T(stack) is the threshold number for a given stack, 
       k1(stack), k2(stack) . . . kn(stack) are functions or constants, possibly for determining proportionality values for each stack, 
       diff(stack)=duration or difference between the present/on-going time period and the time period corresponding to the stack, and 
         N (stack)=number of cards in the stack. 
     It should be noted that other variables, constants, linear equations, non-linear equations, as well as other types of functions can be used in determining threshold function  1136  and/or  1118 . 
     In some embodiments, the probability of a card being included in a group may be determined. For example, the probability of one card associated with past time  1132 B being included in the “1 Day Ago” stack may be greater than the probability of one card associated with present/on-going time  1132 C being included in the “1 Day Ago” stack. Further, consider two cards in present/on-going deck  1132 C: The cards represented by the “T” and “C” where card T is associated with a future time in future time  1132 D, e.g., upon creating a future calendar event associated by card T. As such, card T has a greater probability than card C of being included in future deck  1132 D, possibly after an intervening time period. 
     In some embodiments, a card may be associated with more than one time on a timeline. In such instances, the card may be grouped into more than one group on the timeline. Further, in some instances, the probability of the card being grouped may be determined. For example, consider a scenario with two cards: Card A and card B. Card A may be associated with past time  1132 B and future time  1132 D (e.g., the card was added to timeline  1132  during a time associated with past time  1132 B and relates to an event in future time  1132 D). Card B may be associated with present/on-going time  1132 C and future time  1132 D (e.g., card B was recently added to the timeline and relates to an event in future time  1132 D). When grouping cards for past deck  1132 B, card A may have a greater probability than card B of being grouped in past deck  1132 B. Further, Card B may have a greater probability than card A of being grouped in present/on-going deck  1132 C. Yet further, card A and card B may have equal probabilities of being in grouped in future deck  1132 D. 
     In some embodiments, bundle cards may be outside the view of a timeline. In some instances, the HMD may display the present/on-going time period and time periods near the present/on-going time period, excluding bundle cards in time periods a given duration away from the present/on-going time period. For example, in  FIG. 11D , timeline view  1132   a  may correspond to timeline  1134  as displayed on an HMD. In particular, timeline  1134  may be displayed on the HMD without further instructions by the wearer to view other cards on timeline  1134 . Thus, cards of the “1 Day Ago” stack, the present/on-going deck  1132 C, the “In 1-2 Hrs” stack, and the “Tomorrow” stack of timeline  1132  are displayed in timeline view  1132   a . However, cards in the “&gt;1 Year Ago” stack, “1 Month Ago” stack, “1 Week Ago” stack, “Next Week” stack, and the “&gt;1 Week stack” may not be part of timeline view  1132   a  and may not be displayed on timeline  1134 . 
     As illustrated in  FIG. 11D , the cards of the “1 Day Ago” stack are displayed in timeline  1134  as cards in the “1 Day Ago” deck  11341 . Further, cards in present/on-going deck  1132 C are displayed as cards in present/on-going deck  1134 J. Yet further, cards in the “In 1-2 Hrs” stack and the “Tomorrow” stack are displayed as cards in the “In 2 Days” deck  1134 K. The particular arrangements shown in the  FIGS. 11A-11D  should not be viewed as limiting. It should be understood that other embodiments can include more or less of each element shown in a given figure. Further, some of the illustrated elements can be combined or omitted. Yet further, an example embodiment can include elements that are not illustrated in the figures. 
     In some embodiments, bundle cards and other cards may be simultaneously viewed on a timeline.  FIG. 11E  shows a scenario of a timeline with groups of cards available on the timeline, according to an example embodiment. In scenario  1140 , cards  1142   a ,  1142   b , and  1142   c  may be provided on timeline  1144 B through a computing device with a viewable display, such as an HMD. In particular, card  1142   a  may be associated with a past time period, card  1142   b  may be associated with a present/on-going time period, and  1142   c  may be associated with a future time period. In some instances, cards  1142   a ,  1142   b , and  1142   c  may be spread out along timeline  1144 B such that all three cards are not visible at any given time when viewing timeline  1144 B through the HMD. More specifically, card  1142   a  may have been added to timeline  1144 B three years ago from the present time or present/on-going time period, card  1142   b  may have been added to timeline  1144 B one minute ago from the present time, and card  1142   c  may relate to an event that is scheduled to occur in one year from the present time. However, bundle card  1142   c  may make groups of cards accessible without scrolling through timeline  1144 B. Thus, upon selecting a card with a bundle card indicator  1142   d  on card  1142   c , cards  1142   a ,  1142   b , and  1142   c  may be provided through multi-card content  1144 A displayed on the HMD. 
     In some embodiments, bundle cards may be related to dedicated timelines. As illustrated by timeline  1144 C, bundle card  1142   e  with bundle card indicator  1142   f  may be one of many bundle cards provided by timeline  1144 C. In some embodiments, bundle card  1142   e  may provide some or all of the same information as bundle card  1142   c . Thus, by selecting bundle card  1142   e , cards  1142   a ,  1142   b , and  1142   c  may be provided through multi-card content  1144 D. Bundle cards  1142   c  and  1142   e  may consolidate cards on timelines. In some instances, timeline  1144 C may be displayed on smaller graphic displays such as HMDs, whereas timeline  1144 B may be displayed on larger graphic displays, such as computer monitors. 
     In some embodiments, groups of cards may be managed by data records.  FIG. 11F  shows a scenario of timeline data, according to an example embodiment. For example, scenario  1160  illustrates data records  1152 ,  1154 ,  1156 ,  1158 , and  1160 , accessible as part of timeline data  1150 . It should be noted that each of the data records  1152 ,  1154 ,  1156 ,  1158 , and  1160  may provide data for and correspond to a single card on a timeline. For example, data records  1152 ,  1154 ,  1156 , and  1158  may provide data for cards  1142   a ,  1142   b ,  1142   c , and  1142   e  illustrated in  FIG. 11E , respectively. Further, timeline data  1150  may include data for displaying timeline  1144 B on a graphic display. As such, each data record may correspond to a time when the data record was added to timeline data  1150 . In the example shown in  FIG. 11F , data record  1152  may have been created before data records  1152 - 1160 , data record  1154  may have been created after data record  1152  but before data record  1156 , data record  1156  may have been created after data record  1154  but before data record  1158 , and so on. Further, as shown in  FIG. 11F , present time line  1150 A may illustrate the present time and data records  1158  and  1160  may include events associated with a future time period after the present time associated with present time line  1150 A. 
     In some instances, data records may be linked to other data records. For example, data record  1152  may be linked to data records  1152 A,  1152 C, and  1152 D. Further, data record  1154  may be linked to data records  1154 A,  1154 B, and  1154 C. Yet further, data record  1156  may be linked to data records  1156 B and  1156 D. Yet further, data record  1158  may be linked to data records  1158 A,  1158 B, and  1158 C. In addition, data record  1160  may be linked to data record  1160 C. 
     In some instances, data records may provide a content type of its respective card. For example, data record  1152  may provide content corresponding to a “Phone call from Monica Kim,” as illustrated in data record  1152 A. Further, data record  1152  may be linked with content types of a message and a time as illustrated by data records  1152 C and  1152 D, respectively. 
     In some instances, data provided by data records may be bundled by content type. For example, the data provided by data records  1152 ,  1154 , and  1158  may be bundled into bundle card  1162  since these data records all relate to a single contact, “Monica Kim.” Further, the data provided by data records  1152 C,  1154 B, and  1158 C may be bundled into bundle card  1164  since these data records all include messages. Yet further, the data provided by data records  1152 D,  1154 C, and  1156 D may be bundled into bundle card  1166  since these data records are associated with a specific time. In addition, the content in data records  1156 B,  1158 B, and  1160 C may be bundled into bundle card  1168  since they all are associated with an event. 
     It should be noted that a single card may be bundled into more than one bundle card. As noted, a single data record in timeline data  1150  may represent a card on a timeline. Further, as illustrated in  FIG. 11F , data provided by a single data record may be grouped to multiple bundle cards. For example, data provided from data record  1152  may be copied and bundled into bundle cards  1162 ,  1164 , and  1166 . Therefore, data for a single card may be grouped and bundled in to multiple bundle cards. 
       FIG. 12A  is a flow chart illustrating a method, according to an example embodiment for grouping cards. In  FIG. 12A , method  1200  is described by way of example as being carried out by a computing device, such as a wearable computer, and possibly a wearable computer that includes an HMD. However, it should be understood that example methods, such as method  1200 , can be carried out by a wearable computer without wearing a computing device. For example, such methods may be carried out by simply holding the wearable computer in the wearer&#39;s hands or placing the wearable computer on a platform such as a desk or a table. 
     Further, example methods, such as method  1200 , can be carried out by devices other than a wearable computer, and/or can be carried out by sub-systems in a wearable computer or in other devices. For example, an example method can be carried out by a device such as a mobile phone, which is programmed to simultaneously display a graphic object in a graphic display and also provide a point-of-view video feed in a physical-world window. 
     As shown in  FIG. 12A , method  1200  begins at block  1202 , where a computing device such as an HMD may generate one or more time-stamped bundle cards. In some instances, the one or more time-stamped bundle cards may correspond to a group of cards from a plurality of time-stamped cards. 
     At block  1204 , the computing device may display a user interface for navigation of a chronologically sorted timeline of cards. In some instances, the timeline of cards may span at least a current time period and a first time period, where the timeline includes one or more time-stamped bundle cards and one or more non-bundle cards from the plurality of time-stamped cards. In some instances, a frequency of bundle cards in the first time period may be greater than a frequency of bundle cards in the current time period. 
     In some embodiments, method  1200  may be carried out by a computing device that is configured as a head-mountable device (HMD). In some embodiments, the first time period from method  1200  may be one of a plurality of time periods. In some instances, the plurality of time periods may include at least one of the following: a) a time period at least one year prior to the present/on-going time period, b) a time period at least one month prior to the present/on-going time period, c) a time period at least one week prior to the present/on-going time period, d) a time period at least one day prior to the present/on-going time period, e) a time period at least one hour after the present/on-going time period, f) a time period at least two hours after the present/on-going time period, g) a time period at least one day after the present/on-going time period, and h) a time period at least two days after the present/on-going time period. 
       FIG. 12B  is a flow chart illustrating another method, according to an example embodiment for grouping cards. In  FIG. 12B , method  1210  is described by way of example as being carried out by a computing device, such as a wearable computer, and possibly a wearable computer that includes an HMD, but other techniques and/or device can be used to carry out method  1210 , such as those discussed above in the context of method  1200 . 
     In some embodiments, method  1210  may be performed in relation to method  1200  of  FIG. 12A . In some instances, steps of method  1210  may be combined with that of method  1200 . Further, in some instances, after a computing device performs one or more steps of the method  1200 , the computing device may then perform one or more steps illustrated by method  1210 . 
     As shown in  FIG. 12B , method  1210  begins at block  1212 , where a computing device such as an HMD may determine a plurality of time-stamped cards including one or more cards in a current time period and one or more cards in a first time period. 
     At block  1214 , the computing device may determine respective bundling thresholds for the current time period and the first time period. Further, in some instances, a frequency of time-stamped bundle cards in the first time period may be greater than a frequency of time-stamped bundle cards in the current time period. 
     At block  1216 , the computing device may bundle cards of at least one group from the plurality of time-stamped cards into at least one time-stamped bundle card. 
     At block  1218 , the computing device may display a chronologically sorted timeline of cards that spans at least the current time period and the first time period. In some instances, the timeline may include at least one time-stamped bundle card and at least one time-stamped non-bundle card from the plurality of time-stamped cards. 
     F. Example Visual Stack 
       FIG. 13A  shows that three items are in visual stack  1300  between viewport  1310  and main timeline  1330 : submenu  1320 , contextual menu  1322 , and overlay  1324 . Submenu  1320  includes three images: an image of “Jane Smith,” an image of “Another Person,” and an image associated with “Friends,” with the image of “Another Person” inside the rectangular tube. Contextual menu  1322  includes two options: a “Share” option and a “Delete” option, with the “Share” inside the rectangular tube. Thus, visual stack  1300  shows contextual menu  1322  for a photo bundle card shown on main timeline  1330  with a “Share” option selected from the contextual menu  1322 , and a sharing destination of “Another Person” selected from submenu  1320 . 
       FIG. 13B  shows example visual stack  1350 , according to an example embodiment. From the wearer&#39;s perspective, visual stack  1350  is the collection of images viewed looking down viewport  1360  via a rectangular tube shown with dashed lines in  FIG. 13A , to main timeline  1380 .  FIG. 13B  shows two items are in visual stack  1350  between viewport  1360  and main timeline  1380 : action notification  1370  and overlay  1372 . Action notification  1370  shows a “Send” notification. Thus, visual stack  1300  shows a “Send” notification for a photo bundle card shown on main timeline  1380 . 
     In some embodiments, overlay  1372  is completely opaque with respect to main timeline  1380 . In these embodiments, the wearer viewing visual stack  1350  sees action notification  1370  and overlay  1372 . In other embodiments, overlay  1372  is partially or completely transparent or translucent with respect to main timeline  1380 . In these embodiments, the wearer viewing visual stack  1350  sees action notification  1370  and overlay  1372  with some portion(s) of the photo bundle card shown on main timeline  1380  visible, depending on the visibility of an image on main timeline  1380  through overlay  1372 . 
     G. Conclusion 
     The present disclosure is not to be limited in terms of the particular embodiments described in this application, which are intended as illustrations of various aspects. Many modifications and variations can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. Functionally equivalent methods and apparatuses within the scope of the disclosure, in addition to those enumerated herein, will be apparent to those skilled in the art from the foregoing descriptions. Such modifications and variations are intended to fall within the scope of the appended claims. 
     The above detailed description describes various features and functions of the disclosed systems, devices, and methods with reference to the accompanying figures. In the figures, similar symbols typically identify similar components, unless context dictates otherwise. The example embodiments described herein and in the figures are not meant to be limiting. Other embodiments can be utilized, and other changes can be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are explicitly contemplated herein. 
     With respect to any or all of the ladder diagrams, scenarios, and flow charts in the figures and as discussed herein, each block and/or communication can represent a processing of information and/or a transmission of information in accordance with example embodiments. Alternative embodiments are included within the scope of these example embodiments. In these alternative embodiments, for example, functions described as blocks, transmissions, communications, requests, responses, and/or messages can be executed out of order from that shown or discussed, including substantially concurrent or in reverse order, depending on the functionality involved. Further, more or fewer blocks and/or functions can be used with any of the ladder diagrams, scenarios, and flow charts discussed herein, and these ladder diagrams, scenarios, and flow charts can be combined with one another, in part or in whole. 
     A block that represents a processing of information can correspond to circuitry that can be configured to perform the specific logical functions of a herein-described method or technique. Alternatively or additionally, a block that represents a processing of information can correspond to a module, a segment, or a portion of program code (including related data). The program code can include one or more instructions executable by a processor for implementing specific logical functions or actions in the method or technique. The program code and/or related data can be stored on any type of computer readable medium such as a storage device including a disk or hard drive or other storage medium. 
     The computer readable medium can also include non-transitory computer readable media such as computer-readable media that stores data for short periods of time like register memory, processor cache, and random access memory (RAM). The computer readable media can also include non-transitory computer readable media that stores program code and/or data for longer periods of time, such as secondary or persistent long term storage, like read only memory (ROM), optical or magnetic disks, compact-disc read only memory (CD-ROM), for example. The computer readable media can also be any other volatile or non-volatile storage systems. A computer readable medium can be considered a computer readable storage medium, for example, or a tangible storage device. 
     Moreover, a block that represents one or more information transmissions can correspond to information transmissions between software and/or hardware modules in the same physical device. However, other information transmissions can be between software modules and/or hardware modules in different physical devices. 
     The particular arrangements shown in the figures should not be viewed as limiting. It should be understood that other embodiments can include more or less of each element shown in a given figure. Further, some of the illustrated elements can be combined or omitted. Yet further, an example embodiment can include elements that are not illustrated in the figures. 
     While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.