Patent Publication Number: US-10769883-B2

Title: Method of operating a stack symbols progressive game system, a gaming system and a game controller

Description:
RELATED APPLICATIONS 
     This application is a continuation of and claims priority to U.S. patent application Ser. No. 15/275,079, filed on Sep. 23, 2016, which claims priority to U.S. Provisional Patent Application No. 62/232,726 having a filing date of Sep. 25, 2015, both of which are incorporated herein by reference in their entireties. 
    
    
     BACKGROUND 
     Gaming systems are known that employ stacks of symbols—i.e. groups of the same symbol arranged at contiguous symbol positions on a reel strip. 
     A need exists for alternative gaming systems. 
     BRIEF SUMMARY 
     In a first aspect, the invention provides an electronic method of operating a gaming system comprising a game controller, the method comprising: 
     forming, using the game controller, at least one dynamically generated reel strip by a) conducting a random determination to select one of a plurality of different arrangements of a defined number of stacked symbols, each arrangement dividing the defined number of stacked symbols into a different number of stacks of the symbol, and b) adding the selected arrangement to symbols predefined for the respective reel strip; 
     selecting symbols, using the game controller, from a set of reel strips including the at least one dynamically generated reel strip; 
     displaying the selected symbols on the display; and 
     making, using the game controller, an award if the selected symbols include one or more winning outcomes. 
     In an embodiment, the method comprises conducting a random determination to select a symbol for the stacks of each dynamically generated reel strip for a set of stack symbols. 
     In an embodiment, the method comprises forming dynamically generated reel strips for each of the reel strips. 
     In an embodiment, the random determination from the set of stack symbols is performed independently for each reel strip such that different symbols of the set of stack symbols may be selected for each of the reel strips. 
     In an embodiment, at least one of the winning outcomes requires the portions of the active game area corresponding to respective ones of a defined number of the reel strips to be filled by symbols of a stack of symbols. 
     In an embodiment, the defined number of reel strips is all of the reel strips. 
     In an embodiment, the method comprises selecting, using the game controller, a height for an active game area from one of a plurality of different heights of symbol display positions, and wherein said selecting symbols comprises selecting sufficient symbols to populate the active game area for the current height. 
     In an embodiment, at least some of the different heights are associated with different awards for filling the portions of the active game area corresponding to respective ones of a defined number of the reel strips with symbols of a stack of symbols. 
     In an embodiment, the method comprises selecting the height of the active game area in conjunction with conducting the random determination to select one of a plurality of different arrangements of a defined number of stacked symbols. 
     In an embodiment, the random determination is performed using a weighted table that defines different combinations of arrangements of stacked symbols and heights of the active game area. 
     In a second aspect, the invention provides an electronic gaming system comprising: 
     a display; and 
     a game controller configured to: form at least one dynamically generated reel strip by a) conducting a random determination to select one of a plurality of different arrangements of a defined number of stacked symbols, each arrangement dividing the defined number of stacked symbols into a different number of stacks of the symbol, and b) adding the selected arrangement to symbols predefined for the respective reel strip; 
     select from a set of reel strips including the at least one dynamically generated reel strip; 
     control the display to display the selected symbols; and 
     make an award if the selected symbols include one or more winning outcomes. 
     In a third aspect, the invention provides an electronic game controller for a gaming system comprising a display, the game controller comprising: 
     a reel strip former configured to form at least one dynamically generated reel strip by a) conducting a random determination to select one of a plurality of different arrangements of a defined number of stacked symbols, each arrangement dividing the defined number of stacked symbols into a different number of stacks of the symbol, and b) adding the selected arrangement to symbols predefined for the respective reel strip; 
     a symbol selector for selecting symbols, using the game controller, from a set of reel strips including the at least one dynamically generated reel strip; 
     a display controller configured to control the display to display the selected symbols; and 
     an outcome evaluator configured to make an award if the selected symbols include one or more winning outcomes. 
     In a fourth aspect, the invention provides an electronic method of operating a gaming system comprising a display and a game controller, the method comprising: 
     selecting, using the game controller, a height for an active game area from one of a plurality of different heights of symbol display positions, wherein at least some of the different heights are associated with different awards; 
     selecting, using the game controller, symbols from a plurality of reel strips to populate the active game area for the current height, each reel strip comprising at least one stack of symbols, each symbol of a respective stack being the same; 
     displaying the selected symbols in active game area on the display; and 
     making, using the game controller, an award associated with the current height when the portions of the active game area corresponding to respective ones of a defined number of the reel strips are filled by symbols of a stack of symbols. 
     In an embodiment, the defined number of reel strips is all of the reel strips. 
     In an embodiment, each reel strip comprises at least one stack of symbols having the same length in symbol display positions as the highest possible height of the active game area. 
     In an embodiment, the lengths of the stacks of symbols are dynamically selected from a set of possible lengths. 
     In an embodiment, the smallest possible length of the stacks of symbols corresponds to the highest possible height of the active game area. 
     In an embodiment, the method comprises selecting the lengths of the stacks of symbols and the height of the active display area from a weighted table that defines different combinations of lengths of stacked symbols and heights of the active game area. 
     In a fifth aspect, the invention provides a gaming system comprising: 
     a display; and 
     a game controller configured to: 
     select a height for an active game area from one of a plurality of different heights of symbol display positions, wherein at least some of the different heights are associated with different awards; 
     select symbols from a plurality of reel strips to populate the active game area for the current height, each reel strip comprising at least one stack of symbols, each symbol of a respective stack being the same; 
     control the display to display the selected symbols in active game area; and 
     make the award associated with the current height when the portions of the active game area corresponding to respective ones of a defined number of the reel strips are filled by symbols of a stack of symbols. 
     In a sixth aspect, the invention provides an electronic game controller comprising: 
     a height selector for selecting a height for an active game area from one of a plurality of different heights of symbol display positions, wherein at least some of the different heights are associated with different awards; 
     a symbol selector for selecting symbols from a plurality of reel strips to populate the active game area for the current height, each reel strip comprising at least one stack of symbols, each symbol of a respective stack being the same; 
     a display controller for controlling the display to display the selected symbols in active game area; and 
     an outcome evaluator for making the award associated with the current height when the portions of the active game area corresponding to respective ones of a defined number of the reel strips are filled by symbols of a stack of symbols. 
     In a seventh aspect, the invention provides computer program code which when executed implements the above method. 
     In an eighth aspect, the invention provides a tangible computer readable medium comprising the above program code. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An exemplary embodiment of the invention will now be described with reference to the accompanying drawings in which: 
         FIG. 1  is a block diagram of the core components of a gaming system; 
         FIG. 2  is a perspective view of a standalone gaming machine; 
         FIG. 3  is a block diagram of the functional components of a gaming machine; 
         FIG. 4  is a schematic diagram of the functional components of a memory; 
         FIG. 5  is a schematic diagram of a network gaming system; 
         FIG. 6  is a further block diagram of a gaming system; 
         FIG. 7  is a flow chart of an embodiment; and 
         FIGS. 8A to 8D  are exemplary screen shots showing how the game area changes. 
         FIG. 9  is a table for selection of heights and stacks; and 
         FIG. 10  is table for selection of symbols. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings, there is shown a gaming system having a game controller having components that enable the implementation of a method of operating a gaming system where, in an embodiment, one or more reel strips (advantageously all of the reel strips) are dynamically formed by adding stacked symbols having predefined symbols. In the embodiment, there are different arrangements of the stacked symbols where the stacked symbols are divided into stacks of different lengths. In an embodiment, symbols are selected for display in an active display area which has a height in symbol display positions which is randomly determined from a set of possible heights. In an embodiment, different heights are associated with different awards that are won when stacks of symbols fill the active display area. In an advantageous embodiment, a combination of stacks of different symbols in different columns of the symbol display area can fill the active display area. 
     In advantageous embodiments both the length of the stacks and the height of display area are randomly determined so as to vary the probability of an award being made. In an advantageous embodiment, a weighted table defines combinations of lengths of the reel strips and the height of the symbol display area. 
     General Construction of Gaming System 
     The gaming system can take a number of different forms. In a first form, a standalone gaming machine is provided wherein all or most components required for implementing the game are present in a player operable gaming machine. 
     In a second form, a distributed architecture is provided wherein some of the components required for implementing the game are present in a player operable gaming machine and some of the components required for implementing the game are located remotely relative to the gaming machine. For example, a “thick client” architecture may be used wherein part of the game is executed on a player operable gaming machine and part of the game is executed remotely, such as by a gaming server; or a “thin client” architecture may be used wherein most of the game is executed remotely such as by a gaming server and a player operable gaming machine is used only to display audible and/or visible gaming information to the player and receive gaming inputs from the player. 
     However, it will be understood that other arrangements are envisaged. For example, an architecture may be provided wherein a gaming machine is networked to a gaming server and the respective functions of the gaming machine and the gaming server are selectively modifiable. For example, the gaming system may operate in standalone gaming machine mode, “thick client” mode or “thin client” mode depending on the game being played, operating conditions, and so on. Other variations will be apparent to persons skilled in the art. 
     Irrespective of the form, the gaming system has several core components. At the broadest level, the core components are a player interface  50  and a game controller  60  as illustrated in  FIG. 1 . The player interface is configured to enable manual interaction between a player and the gaming system and for this purpose includes the input/output components required for the player to enter instructions to play the game and observe the game outcomes. 
     Components of the player interface may vary from embodiment to embodiment but will typically include a credit mechanism  52  to enable a player to input credits and receive payouts, one or more displays  54 , a game play mechanism  56  including one or more input devices that enable a player to input game play instructions (e.g. to place a wager), and one or more speakers  58 . 
     The game controller  60  is in data communication with the player interface  50  and typically includes a processor  62  that processes the game play instructions in accordance with game play rules and outputs game play outcomes to the display. Typically, the game play rules are stored as program code in a memory  64  but can also be hardwired. Herein the term “processor” is used to refer generically to any device that can process game play instructions in accordance with game play rules and may include: a microprocessor, microcontroller, programmable logic device or other computational device, a general purpose computer (e.g. a PC) or a server. That is a processor may be provided by any suitable logic circuitry for receiving inputs, processing them in accordance with instructions stored in memory and generating outputs (for example on the display). Such processors are sometimes also referred to as central processing units (CPUs). Most processors are general purpose units, however, it is also know to provide a specific purpose processor using an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA). 
     A gaming system in the form of a standalone gaming machine  10  is illustrated in  FIG. 2 . The gaming machine  10  includes a console  12  having a display  14  on which are displayed representations of a game  16  that can be played by a player. A mid-trim  20  of the gaming machine  10  houses a bank of buttons  22  for enabling a player to interact with the gaming machine, in particular during game play. The mid-trim  20  also houses a credit input mechanism  24  which in this example includes a coin input chute  24 A and a bill collector  24 B. Other credit input mechanisms may also be employed which may receive physical items other than coins or bills, for example, a card reader for reading a smart card, debit card or credit card. Likewise, other credit input mechanisms may be employed for receiving tickets such that a ticket reader reads tickets having a value and crediting the player based on the face value of the ticket. A player marketing module (not shown) having a reading device may also be provided for the purpose of reading a player tracking device, for example as part of a loyalty program. The player tracking device may be in the form of a card, flash drive or any other portable storage medium capable of being read by the reading device. In some embodiments, the player marketing module may provide an additional credit mechanism, either by transferring credits to the gaming machine from credits stored on the player tracking device or by transferring credits from a player account in data communication with the player marketing module that is accessed in response to insertion of the player tracking device. 
     A top box  26  may carry artwork  28 , including for example pay tables and details of bonus awards and other information or images relating to the game. Further artwork and/or information may be provided on a front panel  29  of the console  12 . A coin tray  30  is mounted beneath the front panel  29  for dispensing cash payouts from the gaming machine  10 . 
     The display  14  shown in  FIG. 2  is in the form of a liquid crystal display. The display  14  may any other suitable video display unit, such as an OLED display. The top box  26  may also include a display, which may be of the same type as the display  14 , or of a different type. 
       FIG. 3  shows a block diagram of operative components of a typical gaming machine which may be the same as or different than the components of the gaming machine of  FIG. 2 . 
     The gaming machine  100  includes a game controller  101  having a processor  102  mounted on a circuit board. Instructions and data to control operation of the processor  102  are stored in a memory  103 , which is in data communication with the processor  102 . Typically, the gaming machine  100  will include both volatile and non-volatile memory and more than one of each type of memory, with such memories being collectively represented by the memory  103 . 
     The gaming machine has hardware meters  104  for purposes including ensuring regulatory compliance and monitoring player credit, and an input/output (I/O) interface  105  for communicating with peripheral devices of the gaming machine  100 . The input/output interface  105  and/or the peripheral devices may be intelligent devices with their own memory for storing associated instructions and data for use with the input/output interface or the peripheral devices. A random number generator module  113  generates random numbers for use by the processor  102 . Persons skilled in the art will appreciate that the reference to random numbers includes pseudo-random numbers. 
     In the example shown in  FIG. 3 , a player interface  120  includes peripheral devices that communicate with the game controller  101  including one or more displays  106 , a touch screen and/or buttons  107  (which provide a game play mechanism), a card and/or ticket reader  108 , a printer  109 , a bill acceptor and/or coin input mechanism  110  and an output mechanism  111  (which causes output of coins via coin tray  30  or output of a ticket via printer  109 , and the like). Additional hardware may be included as part of the gaming machine  100 , or hardware may be omitted as required for the specific implementation. For example, while buttons or touch screens are typically used in gaming machines to allow a player to place a wager and initiate a play of a game, any input device that enables the player to input game play instructions may be used. For example, in some gaming machines a mechanical handle is used to initiate a play of the game. Persons skilled in the art will also appreciate that a touch screen can be used to emulate other input devices, for example, a touch screen can display virtual buttons which a player can “press” by touching the screen where they are displayed. 
     In addition, the gaming machine  100  may include a communications interface, for example a network card  112 . The network card may, for example, send status information, accounting information or other information to a bonus controller, central controller, server or database and receive data or commands from the bonus controller, central controller, server or database. In embodiments employing a player marketing module, communications over a network may be via player marketing module—i.e. the player marketing module may be in data communication with one or more of the above devices and communicate with it on behalf of the gaming machine. The network card may provide value output information, as well, such as credits or currency information. 
       FIG. 4  shows a block diagram of the main components of an exemplary memory  103 . The memory  103  includes RAM  103 A, EPROM  103 B and a mass storage device  103 C. The RAM  103 A typically temporarily holds program files for execution by the processor  102  and related data. The EPROM  103 B may be a boot ROM device and/or may contain some system or game related code. The mass storage device  103 C is typically used to store game programs, the integrity of which may be verified and/or authenticated by the processor  102  using protected code from the EPROM  103 B or elsewhere. 
     It is also possible for the operative components of the gaming machine  100  to be distributed, for example input/output devices  106 ,  107 ,  108 ,  109 ,  110 ,  111  to be provided remotely from the game controller  101 . 
       FIG. 5  shows a gaming system  200  in accordance with an alternative embodiment. The gaming system  200  includes a network  201 , which for example may be an Ethernet network. Gaming machines  202 , shown arranged in three banks  203  of two gaming machines  202  in  FIG. 5 , are connected to the network  201 . The gaming machines  202  provide a player operable interface and may be the same as the gaming machines  10 , 100  shown in  FIGS. 2 and 3 , or may have simplified functionality depending on the requirements for implementing game play. While banks  203  of two gaming machines are illustrated in  FIG. 5 , banks of one, three or more gaming machines are also envisaged. 
     One or more displays  204  may also be connected to the network  201 . For example, the displays  204  may be associated with one or more banks  203  of gaming machines. The displays  204  may be used to display representations associated with game play on the gaming machines  202 , and/or used to display other representations, for example promotional or informational material. 
     In a thick client embodiment, game server  205  implements part of the game played by a player using a gaming machine  202  and the gaming machine  202  implements part of the game. With this embodiment, as both the game server and the gaming device implement part of the game, they collectively provide a game controller. A database management server  206  may manage storage of game programs and associated data for downloading or access by the gaming devices  202  in a database  206 A. Typically, if the gaming system enables players to participate in a Jackpot game, a Jackpot server  207  will be provided to perform accounting functions for the Jackpot game. A loyalty program server  212  may also be provided. 
     In a thin client embodiment, game server  205  implements most or all of the game played by a player using a gaming machine  202  and the gaming machine  202  essentially provides only the player interface. With this embodiment, the game server  205  provides the game controller. The gaming machine will receive player instructions, pass these to the game server which will process them and return game play outcomes to the gaming machine for display. In a thin client embodiment, the gaming machines could be computer terminals, e.g. PCs running software that provides a player interface operable using standard computer input and output components. Other client/server configurations are possible, and further details of a client/server architecture can be found in WO 2006/052213 and PCT/SE2006/000559, the disclosures of which are incorporated herein by reference. 
     Servers are also typically provided to assist in the administration of the gaming network  200 , including for example a gaming floor management server  208 , and a licensing server  209  to monitor the use of licenses relating to particular games. An administrator terminal  210  is provided to allow an administrator to run the network  201  and the devices connected to the network. 
     The gaming system  200  may communicate with other gaming systems, other local networks, for example a corporate network, and/or a wide area network such as the Internet, for example through a firewall  211 . 
     Persons skilled in the art will appreciate that in accordance with known techniques, functionality at the server side of the network may be distributed over a plurality of different computers. For example, elements may be run as a single “engine” on one server or a separate server may be provided. For example, the game server  205  could run a random generator engine. Alternatively, a separate random number generator server could be provided. Further, persons skilled in the art will appreciate that a plurality of game servers could be provided to run different games or a single game server may run a plurality of different games as required by the terminals. 
     Further Details of the Gaming System 
     The player operates the game play mechanism  56  ( FIG. 1 ) to specify a wager which will be evaluated for this play of the game in accord with credit input made via credit input mechanism  52  which may establish a credit balance. The credit balance may increase and decrease based on wager input, awards of the game, etc. Game play mechanism  56  is also operated by the player to initiate a play of the game. Persons skilled in the art will appreciate that a player&#39;s wager can be varied from game to game dependent on player selections. In most spinning reel games, it is typical for the player&#39;s wager to be made up of a selection as to how the game outcome will be evaluated by specifying what parts of the game outcome will qualify for winning outcomes and a multiplier that will apply to each winning outcome. For example, a player&#39;s wager may be based on how many lines the player plays in each game—e.g. a minimum of one line up to the maximum number of lines allowed by the game (noting that not all permutations of win lines may be available for selection) and an amount per line—e.g. one, two or five credits. Winning outcomes on an activated win line may be evaluated based on a pay table that specifies the amount awarded for a one credit per line wager multiplied by the amount wagered per line. 
     Such win lines are typically formed by a combination of symbol display positions, one from each reel, the symbol display positions being located relative to one another such that they form a line. 
     In many games, the gaming machine may award winning outcomes which are not strictly limited to the lines they have selected, for example, “scatter” pays are awarded independently of a player&#39;s selection of pay lines. 
     Persons skilled in the art will appreciate that in other embodiments, the player may select a number of reels to play. Games of this type are marketed under the trade name “Reel Power” by Aristocrat Leisure Industries Pty Ltd and are also known as “ways” to win games. The selection of the reel means that each displayed symbol of the reel can be substituted for a symbol at one or more designated display positions. In other words, all symbols displayed at symbol display positions corresponding to a selected reel can be used to form symbol combinations with symbols displayed at a designated, symbol display positions of the other reels. For example, if there are five reels and three symbol display positions for each reel such that the symbol display positions comprise three rows of five symbol display positions, the symbols displayed in the center row are used for non-selected reels. As a result, the total number of ways to win is determined by multiplying the number of active display positions of each of the reels, the active display positions being all display positions of each selected reel and the designated display position of the non-selected reels. As a result, for five reels and fifteen display positions there are 243 ways to win. 
     In  FIG. 6 , the processor  62  of game controller  60  is shown implementing a number of modules based on program code and data stored in memory  64 . Persons skilled in the art will appreciate that one or more of the modules could be implemented in some other way, for example by a dedicated circuit. 
     The outcome generator  622  is configured to form reel strips dynamically during each play of the game by determining an arrangement of stacks of symbols to be added to predefined base reel strips. That is, each time a player places a fresh wager, one or more reel strips are dynamically formed by adding stacks of symbols to base reel strips. In this embodiment, the outcome generator  622  is also configured to determine a height for the displayed game play area that will be active in a current game. In the embodiment, the height of the displayed game area (in terms of the number of rows of symbols displayed) and the length of stacks (in terms of the number of symbols in a stack) are selected from a single, co-dependent weighted table in order to allow design of a game in which occurrences of long stacks and increases in game height both occur relatively frequently. To this end, the outcome generator  622  includes a stacked symbol arrangement and height selector  622 A which selects one of a combination of game area heights (e.g., in terms of rows in an array) and stack length arrangements (e.g., in terms of the number of symbols in the stack) from a weighted table  642 . 
     In this embodiment, the game area defines the number of symbol display positions that will be displayed in a particular play of the game on display  54 . The game play area has a number of columns corresponding to respective ones of a plurality of reel strips. In one example, shown in  FIG. 8A , there are five columns of symbol display positions  821 ,  822 ,  823 ,  824  and  825 . The symbol display positions are arranged in a rectangular array (a 5×5 array) with five rows of symbol display positions. This is one example of a lowest number of rows, as shown in  FIG. 8A . Accordingly, it will be appreciated that if there are five rows, the height of the active game area is five symbol positions high. 
     In one example, shown in  FIGS. 8A to 8D  there are four possible different heights of the active game play area, i.e., five symbol positions high, six symbol positions high, seven symbol positions high and eight symbol positions high, shown in  FIGS. 8A to 8D  respectively. In one example, there are also four possible different arrangements of stacks. In the embodiment, each arrangement of stacks is formed by dividing a defined number of stacked symbols into different numbers of stacks of the symbol. In one example, there are forty-eight symbols that are added to each of the five reels in particular stack arrangements. 
     In this respect, symbol data  641  defines base reel strips  641 A which are comprised of a number of predefined symbols (e.g., 35 symbols) to which arrangements of stacked symbols will be added. The base reel strips  641 A also define the positions at which the stacks of symbols will be inserted, e.g., at any one of the reel positions, e.g., at 35 different locations between the 35 base symbols on a reel. Alternatively, the positions at which stacks may be inserted may be less than 35 and be predefined positions. In one example, 48 symbols are inserted into each reel and there are four possible arrangements of symbols: (1) two stacks which are 24 symbols long, (2) three stacks which are 16 symbols long, (3) four stacks which are 12 symbols long, and (4) six stacks which are 8 symbols long. In this example, while each stack arrangement of a specific reel will have the same number of stacked symbols, a different number of stacked symbols  641 B may be selected for different reels. In this embodiment of the invention, the same arrangement of stacked symbols is applied to each reel. 
     The outcome generator has a stacked symbol selector  622 C which obtains a number from random number generator  621  in order to select one (e.g., a Batman symbol) of a plurality of stackable symbols  641 B (e.g., a Batman symbol, a Robin symbol a Batgirl symbol and a Cat woman symbol) to be added to the individual reels  821 - 825 . The stackable symbols  641 B are a subset of the base game symbols used during play of the game. 
     It will be appreciated that in an alternate embodiment, a single weighted table could be employed which defines not only the arrangement of stacks and the height of the game area but also which symbols will be added in stacks and into which reels. 
     In the embodiment, once the stacked symbol arrangement and height selector  622 A has selected the stacked symbol arrangement and the active game area height, and the stacked symbol selector  622 C has selected the stacked symbols for the respective reels, the reel strip former  622 D combines these selections with a base reel strip  641 A to form a reel strip  641 C. 
     It will be appreciated that the particular approach of separately selecting stacked symbols for all of the reels allows for an advantageous award making technique in gaming systems of embodiments of the invention as described in further detail below. However, in other embodiments, less than all of the reels could have stacks of symbols added or the same symbol could be added to all of the reels. 
     Once the reel strips are formed, a symbol selector  622 B selects symbols from the formed reel strips  641 C using random number generator  621 . The selected symbols are advised to the display controller  624  which causes them to be displayed on display  54  at a set of display positions. 
     One example of selecting symbols is for the symbol selector  622 B to select symbols from the formed reel strips  641 C corresponding to respective ones of a plurality of spinning reels. The formed reel strips  641 C specify a sequence of symbols for each reel. In an embodiment, the symbol selector  622 B selects the symbols for display by selecting a reel stopping position in the sequence. It is known to use a probability table stored in memory  64  to vary the odds of a particular reel stop position being selected. Other techniques can be used to control the odds of particular outcomes occurring to thereby control the return to player of the game. 
     Once symbols are selected (for display), they are evaluated in order to determine whether they include any winning outcomes. For example, in  FIG. 8A , there is shown a winning combination  831  which is highlighted in the selected symbols. Another winning outcome  832  is highlighted in  FIG. 8D . These evaluations are made by outcome evaluator  623  based on the pay table  643  which defines the winning outcomes and associated awards. In some embodiments, the outcome evaluator  623  also determines whether the active game area for the current height is completely populated by symbols from the stacks of symbols and makes an award of a progressive feature game as described in further detail below. 
     In this respect, referring to  FIGS. 8A-8D  there are shown a plurality of screen shots  800 A to  800 D of a game with the active game area in a number of different states. In each of the screen shots, the symbols are displayed in five columns  821 ,  822 ,  823 ,  824  and  825  of symbol display positions.  FIGS. 8A-8D  show four different heights of the active game play area. In  FIG. 8A , the active game play area  861  is five symbol positions high. In  FIG. 8B , the active game play area  862  is six symbol positions high. In  FIG. 8C , the active game play area  863  is seven symbol positions high. In  FIG. 8D , the active game play area  864  is eight symbol positions high. 
     In the example, there are four progressive jackpot prizes, a Batman jackpot  811 , a Batgirl jackpot  812 , a Cat woman jackpot  813 , and a Robin jackpot  814 . In the example, an award of a progressive feature from which these jackpots can be won is linked to the current height of the active game play area. Thus, the height of the active game area is part of an indication to which progressive jackpot is currently available. 
     In  FIG. 8A , where the height is five symbols high, the Robin progressive jackpot  814  can be triggered as further indicated by the word Robin  871  being placed alongside the game play area. In  FIG. 8B , the Cat woman progressive jackpot  813  is available as additionally indicated by the word Cat woman  872 . In  FIG. 8C , the Batgirl progressive jackpot  812  is available as additionally indicated by the message Batgirl  873 . In  FIG. 8D , the Batman progressive jackpot  811  is available as additionally indicated by the word Batman  874 . 
     Thus, advantageously, the height of the active game play area  861 - 864  indicates the available progressive feature. While in this example, a separate progressive feature is carried out by the progressive feature controller  622 E in order to determine whether to award a current value of the respective progressive jackpot prize  811 - 814 , and hence this is what is awarded. In another embodiment, the progressive prize could be awarded directly without a feature game. 
     In this respect, in embodiments of the invention, the award criterion is that a defined number of columns of symbol display positions (advantageously all of the columns) are filled with a stack of symbols irrespective of whether different symbols provide the stack in different columns. For example, referring to  FIG. 8B , it will be apparent that there is a stack  852  of Robin symbols filling the first column  821  and stacks  853 ,  854  of Batgirl symbols filling columns  822  and  823 . Both Robin and Batgirl stacks count towards an award in embodiments of the invention, even though they are different. In other of the Figures, stacks of other stackable symbols such as Cat woman symbols  851  and Batman symbols  855  are shown filling an entire column. 
     As indicated above, in an advantageous embodiment of the invention, it is a requirement that all of the portions of the active game area that correspond to respective ones in different reels are filled with stacks of symbols for there to be an award by outcome evaluator  623 , however, the individual symbols of different stacks may be different. In other embodiments, it may be sufficient that a smaller number of portions of the game play area are filled by stacks, for example, the three filled columns of the game play area shown in  FIG. 8B or 8D . 
     It will be appreciated that the combination of the arrangement of stacked symbols in terms of their length and the height of the area controls the probability of a progressive feature award being made. For example, with an area height of eight rows, symbol stacks of 24 symbols are more likely to fill an entire column of the area array than a symbol stack of 8 symbols. The stacks when added to the 35 base symbols are preferably spread apart as much as possible. With six stacks, a stack may be placed every six symbols except the last being placed after 5 symbols. 
     Referring again to  FIG. 6 ,  FIG. 6  shows that the progressive prizes  645  are stored in memory  64  of the gaming system. They are then awarded from the progressive feature by progressive feature controller  622 E as described above. Any award of a prize is added to the meters  644 . In this respect,  FIGS. 8A to 8D  show a bet meter  841 , a win meter  842 , and a credit meter  843 . Typically, a win will be awarded to a win meter; however, in some embodiments, an award of above a certain size may be awarded directly to the credit meter to prevent it being used in any gamble feature that forms part of the game. In other embodiments, the progressive prizes could be part of a link game in which a number of different gaming machines compete to win the same prize. For example, a bank of four gaming machines may have a common link controller. The weight column in table  901  has a weight indicated at each of the 16 height/stack arrangements (although the grayed-out portions show a “2” as the weight merely for exemplary purposes). 
     The following table is an example different than  FIG. 10  in which patterns and their weights are shown without use of numbers with symbol names. 
                            Symbol insertion:                                     Reel 1   Reel 2   Reel 3   Reel 4   Reel 5   Weight               R1   Batgirl   R1   Batgirl   R1   5       R2   R2   Robin   Robin   Robin   6       R1   R1   R1   R1   Cat   4                       woman       R2   R2   R1   R1   Batman   5                    
The table above shows, in its far right column, a total weight of 20 (5+6+4+5=20). Thus, the first row indicates a weight of 5 in the far right column, meaning that 5 out of 20, or 25% of the time, on any given spin it is likely that (as shown in row 1) symbol R1 will be inserted into reels 1, 3 and 5 while simultaneously “Batgirl” will be inserted into reels 2 and 4. As will suggest itself, other forms of tables may be used for weighted symbol insertion.
 
     Referring to  FIG. 7 , there is shown a method  700  of the embodiment. At step  705 , a wager is received and a player initiates a play of the game. At step  710 , a height-and-symbol arrangement is selected from a weighted table  642  of combinations of game area heights and stack length arrangements. An example table  901  of the table  642  is shown in  FIG. 9 . Four different reel heights (5 rows, 6 rows, 7 rows, 8 rows) are shown together with the number of stacks available for each reel height, i.e., sixteen different selections are available for random selection. However, each selection may be weighted. A reel height of five and number of stacks of six is shown with a weight of 1; whereas, a reel height of seven with three stacks is shown with a weight of 4. Thus, there is four times the chance of randomly selecting the reel height of seven and three stacks as there is in randomly selecting the reel height of five with six stacks. The weight column in table  901  has a weight associated with each of the 16 height/stack arrangements (although only two weights are shown in  FIG. 9 ). 
     Referring again to  FIG. 7 , at step  715 , a symbol is selected to be stacked for each reel. As shown in  FIG. 10 , a table  1001  illustrates ten different symbols  1003  that may be selected. Each symbol  1003  is associated with a single number 0 through 9 in a set  1005 . A single number 0 through 9 is randomly selected for indicating its associated symbol  1003  for selection. In the embodiment, the selected symbol  1003  is the only symbol that occurs in each of the symbol stacks for one reel. 
     Referring again to  FIG. 7 , at step  720 , the reels are formed. At step  725 , the symbol selector  622 B then selects the symbols for the game, e.g., by spinning and stopping the reels for display in the current game area. 
     At step  730 , the outcome evaluator  623  evaluates the symbols selected at step  725  against the pay table. Also, evaluator  623  determines whether the stacks in the selected displayed symbols fill all symbol positions of a defined number of reels. For example, where three of the five reels only contain stacks, evaluator  623  may be configured to require one, two or three reels to only contain stacks. The outcome evaluator  623  awards the progressive feature from which the player may win the progressive corresponding to the current height, at step  740 . The method then involves conducting the progressive feature game (e.g., a pick-a-box game where the plyer has a defined number of picks to find a jackpot awarding symbol) and upon the progressive being won, at step  750 , the progressive prize is awarded at step  755 . The method ends at step  760 . 
     In some embodiments, an eligibility criterion may be applied in order for the player to be eligible for stacks of symbols to be added and/or for the game area to change height. For example, the player may be eligible based on the player making a certain sized wager, making an ante bet, selecting all win lines, playing sufficient games, or that the player is a member of a loyalty program. 
     Thus, at the start of each spin, the reels will be changed by inserting stacks of repeated symbols into the reels at semi-random points along the reels. It is a semi-random insertion in that the first position is randomly chosen and the following positions are chosen to maximize the distance between stacks on the reel. The lengths of these insertions are the same from reel to reel, but not from spin to spin. That is, at each spin the length of stacks is randomly selected. The symbols being inserted may also change from reel to reel and spin to spin. 
     The position of insertion, the symbols inserted, and number of occurrences of that symbol, are determined in three steps. Initially, the particular symbol to be inserted into each reel at the insertion point is randomly determined, for example using a table  1001  ( FIG. 10 ). Next, the game height and the length of the stacks being inserted is randomly selected, for example, using table  901  ( FIG. 9 ). The height and stack size are determined simultaneously by a single selection from a weighted table. In the embodiment, forty-eight symbols will always be inserted on a given reel and they will be: two stacks of 24, three stacks of 16, four stacks of 12 or six stacks of 8. Next, a random starting insertion point is determined on each reel. All points on the reel are equally likely to be determined. From the starting insertion point, the reel is divided into a number of approximately equal sections with said number being equal to the number of stacks determined to be inserted. For example, reel 1 has a length of 35 symbols. A random number between 0 and 34 (inclusive) is generated. For example, the number 11 is generated. Then, if 4 stacks of 12 symbols high were determined, then preferred insertion points would be: 11, 20, 29 and 2. 
     Next a check is performed to determine whether the insertion points are allowed. A stack of a given symbol cannot be inserted next to the same symbol. If, in our current example, the symbols to be inserted between points 11 and 12 match the base symbol located at point 12, the stack would be moved for insertion between points 10 and 11. If the symbols to be inserted between points 11 and 12 match the base symbol located at point 11, the stack would be moved for insertion between points 12 and 13. This adjustment does not change the preferred placement between points 20 and 21 for insertion at point 20, but this position, too, must be checked in the same manner so as not to insert the stack next to the same symbol. 
     Persons skilled in the art will appreciate that rather than a progressive feature game from which a progressive prize can be won, the filling of columns with stacks of symbols can be used to trigger some other form of feature game. A feature game involves some additional elements of game play which usually only occurs when a trigger condition is met (in this case based on stacks filling the game play area). Types of feature games include: those where a series of free game events are awarded such as free games or re-spins (where some reels are held while others are re-spun); games where the symbols on the reel are changed; and “second screen” games where game play is totally different to the base game, for example where the player makes selections in a “pick a box type” game. Further, the progressive feature need not be the only feature game. 
     Typically, a winning outcome will result in some forms of awards being made such as an award of credits. Such an award may never actually be physically received by a player. For example, many gaming systems provide a player with a double or nothing gamble feature, where the player can double or forfeit their credits before commencing another play of the game or cashing out. Further, as credits are fungible, once credits have been added to the credit meter it is not possible to distinguish between credits which exist because the player has input cash or the like and credits resulting from an award. 
     Further aspects of the method will be apparent from the above description of the system. It will be appreciated that at least part of the method will be implemented electronically, for example, digitally by a processor executing program code such as in the above description of a game controller. In this respect, in the above description certain steps are described as being carried out by a processor of a gaming system, it will be appreciated that such steps will often require a number of sub-steps to be carried out for the steps to be implemented electronically, for example due to hardware or programming limitations. For example, to carry out a step such as evaluating, determining or selecting, a processor may need to compute several values and compare those values. 
     Example 
     In an example of an embodiment of the invention, the method of operating a gaming system involves: 
     1) Inserting stacks of varying length; 
     2) Varying the height of the game play area of varying height; 
     3) Requiring that the game area be filled with stacks to trigger the award of progressive jackpot prizes; and 
     4) Using the game height to both indicate and determine which Progressive is eligible. 
     In the example, the choice of symbols to be inserted onto the reels is made by the game controller using weighted tables of symbol combinations. In this way, the stacked symbols are placed into the game in a random manner. In one example, there are 35 fixed symbols on each reel. 48 symbols will be inserted into each of those reels to dynamically form the reel. By a random determination, they will be placed as one of the following: 2 stacks 24 symbols long, 3 stacks of 16 symbols, 4 stacks of 12 symbols, or 6 stacks of 8 symbols. Controlling the height of the stacks allows control of the probability of stopping the reel with the active game area filled with the same symbol. For example, for a game play area of height 8 symbol display positions (the maximum height of the game play area in this example), it is much less likely to fill with stacks of length 8 than it is with stacks of length 24. In this example, the weighted table is arranged such that different symbols of the symbols that can be stacked can be selected for each reel. 
     The gaming system indicates an “Active Progressive Level” by means of an “Active Game Height”. Simply stated, the Active Game Height dictates the eligible progressive level for this spin of the base game. That is, there is a different progressive prize associated with each of the heights, with the highest progressive prize associated with the highest height and the lowest prize associated with the lowest height. Prior to the actual spin, all game heights and all levels of the Progressive are possible. In the example, after the start of the spin, if the game is only 5 symbol positions tall, only the lowest level of the 4-level Progressive is possible. Similarly, a 6 high game has the possibility of awarding the second smallest progressive, and so forth for the next two levels. 
     The Progressive Feature is triggered (awarded) when the active game area of each reel (individually) is filled with the same symbol. That is, filling the active game area is a winning outcome that results in the award of the Feature. While in the example, the award is the conduct of a Progressive Feature which may or may not result in the award of the progressive prize, in other examples, an award (e.g. in credits) may be made directly in response to filling the active game area. 
     In the example, the active game area of each reel is individually filled in the sense that different symbols may fill each reel. To clarify, if the active game area of reel 1 is filled with symbol A, reel 2 filled with symbol B, reel 3 filled with symbol C, reel 4 filled with symbol D, and reel 5 filled with symbol E, the Progressive Feature tied to the current Game Height will be triggered. The symbols on reel 1 do not have to match those on reel 2. This is advantageous because in most stacking games, the player loses interest as soon as they see non-differing stacked symbols on reels 1 and 2, whereas in the present method the player can still achieve a win in this circumstances. 
     In the example, the Game Height and Stack Length are selected from a single, co-dependent weighted table. This is advantageous because if the stack length and the game height were determined independently, it would be necessary to greatly limit both the occurrences of long stacks and the increases in game height. By making it more likely that the largest game height and the shortest stacks appear together, it is possible to show more games of maximum height without over paying. 
     As indicated above, the method may be embodied in program code. The program code could be supplied in a number of ways, for example on a tangible computer readable storage medium, such as a disc or a memory device, e.g. an EEPROM, (for example, that could replace part of memory  103 ) or as a data signal (for example, by transmitting it from a server). Further different parts of the program code can be executed by different devices, for example in a client server relationship. Persons skilled in the art will appreciate that program code provides a series of instructions executable by the processor. 
     It will be understood to persons skilled in the art of the invention that many modifications may be made without departing from the spirit and scope of the invention, in particular it will be apparent that certain features of embodiments of the invention can be employed to form further embodiments. 
     It is to be understood that, if any prior art is referred to herein, such reference does not constitute an admission that the prior art forms a part of the common general knowledge in the art in any country. 
     In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.