A computer-implemented method comprising: receiving a first gesture, at least a portion of the first gesture being over a first user interface associated with a first application; determining whether a start point of the first gesture is an edge; in response to determining that the start point of the first gesture is not an edge, passing the first gesture to the first application; in response to determining that the start point of the first gesture is an edge, determining whether a line from the start point to a later point of the first gesture is approximately perpendicular to the edge; and in response to determining that the line is not approximately perpendicular to the edge, passing the first gesture to the first application; and in response to determining that the line is approximately perpendicular to the edge, determining a factor of the first gesture, determining whether to present an application-selection user interface presented by a system-interface module or a system-control user interface presented by the system-interface module to present based on the determined factor of the first gesture, in response to determining to present the application-selection user interface, passing the first gesture to the application-selection user interface and presenting the application-selection user interface on a display, the application-selection user interface having thumbnail images for applications, each of the thumbnail images a visual representation of an application interface for a respective one of the applications; receiving a selection of one of the thumbnail images and through a second gesture or the later point of the first gesture, the second gesture or later point of the first gesture portion dragging the selected thumbnail image from the user interface to a region of the display based at least in part, on the second gesture or the later point of the first gesture; and responsive to receiving the selection and based on the region of the display to which the selected thumbnail image is dragged, presenting the application interface associated with the selected thumbnail image at a size and location in part of the region, the presenting effective to enable interaction with a selected application associated with the selected thumbnail image. receiving a first gesture, at least a portion of the first gesture being over a first user interface associated with a first application; determining whether a start point of the first gesture is an edge; in response to determining that the start point of the first gesture is not an edge, passing the first gesture to the first application; in response to determining that the start point of the first gesture is an edge, determining whether a line from the start point to a later point of the first gesture is approximately perpendicular to the edge; and in response to determining that the line is not approximately perpendicular to the edge, passing the first gesture to the first application; and in response to determining that the line is approximately perpendicular to the edge, determining a factor of the first gesture, determining whether to present an application-selection user interface presented by a system-interface module or a system-control user interface presented by the system-interface module to present based on the determined factor of the first gesture, in response to determining to present the application-selection user interface, passing the first gesture to the application-selection user interface and presenting the application-selection user interface on a display, the application-selection user interface having thumbnail images for applications, each of the thumbnail images a visual representation of an application interface for a respective one of the applications; receiving a selection of one of the thumbnail images and through a second gesture or the later point of the first gesture, the second gesture or later point of the first gesture portion dragging the selected thumbnail image from the user interface to a region of the display based at least in part, on the second gesture or the later point of the first gesture; and responsive to receiving the selection and based on the region of the display to which the selected thumbnail image is dragged, presenting the application interface associated with the selected thumbnail image at a size and location in part of the region, the presenting effective to enable interaction with a selected application associated with the selected thumbnail image.