WO2008055321A1

WO2008055321A1 - Gaming machine with bonus feature

Info

Publication number: WO2008055321A1
Application number: PCT/AU2007/001902
Authority: WO
Inventors: Andrew Brian Masen
Original assignee: Stargames Corporation Pty Limited
Priority date: 2006-11-10
Filing date: 2007-12-11
Publication date: 2008-05-15
Also published as: AU2006235984A1

Abstract

A gaming machine is provided. The gaming machine includes a display and a wager acceptor for receiving wagers from a player for a primary game. The gaming machine further includes a game controller which is arranged to produce a primary game outcome, cause the display to display the primary game outcome and award any winnings from the outcome of the primary game to the player. The primary game is capable of producing a trigger outcome which causes the controller to provide a bonus feature. In the bonus feature, the controller causes the display to display a plurality of indicia (40), at least some indicia concealing a bonus prize. Randomly selecting one or more of the indicia (40), causes the display to reveal the respective concealed bonus prize(s) and awards the revealed bonus prize(s) to the player. The a) the number of indicia (40) selected and revealed; b) the distribution and/or number of selectable indicia (40); c) the probability of prizes available in exposable indicia (40); and/or d) the value of exposable prizes, can be varied with respect to the size of the size of the player's wager. A method for operating the gaming machine is also provided

Description

GAMING MACHINE WITH BONUS FEATURE FIELD OF THE INVENTION

The present invention relates to gaming machines and, in particular, to a bonus feature in a gaming machine. BACKGROUND TO THE INVENTION

Slot and poker machines have long been known and many variations in both their physical characteristics and the game types playable have been developed.

Such machines generally include a plurality of parallel reels, either physical or electronically simulated, having a plurality of faces on which symbols are disposed. The reels (which, as used hereinafter, may include either mechanical reels or simulations thereof shown on a video display device) are mounted to rotate around a common axis. Upon actuation of a gaming cycle, the reels rotate until being stopped in a position exposing various groupings of symbols. For example, three symbols vertically per reel may be exposed such that the upper, middle and lower symbols of respective faces of each reel coincide to form a vertical line and the result of which is to display an array of symbols for each gaming cycle. The symbols are usually brightly colored and easily recognizable, such as images of fruits, and simple shapes such as bells, diamonds, or hearts. In the art, it is known to provide pay combinations for the appearance of a predetermined number of symbols across one pay line of the array of symbols displayed. Most games have a variety of winning combinations of symbols, which are often posted on the face of the machine. If the displayed symbols match one of the winning combinations, the player receives a prize (e.g., a cash award or some other award of value, such as extra games).

The winning combinations of symbols are typically determined by evaluating the displayed symbols on one or more "pay lines." Pay lines are either straight or zig-zagged lines that extend between opposing outer reels, crossing through one exposed symbol on each reel. The symbols on each line thus form a pay line combination of symbols which are compared with preset winning combinations to determine whether the pay line combination matches one of the winning combinations. Prizes are awarded to players at the conclusion of a gaming cycle corresponding to the symbols in each pay tine meeting set criteria.

Gaming machines have become more sophisticated and the maximum number of pay lines playable during a gaming cycle on a typical gaming machine can exceed fifteen. As shown in Fig. 1 , each one pay line is defined by forming a continuous line from a predetermined face on, for example, the left outermost reel 10 to a predetermined face on the right outermost reel 14. An example is illustrated schematically in Fig. 1 showing eight possible lines 1-8 playable during a gaming cycle. Prizes are awarded to players at the conclusion of a gaming cycle corresponding to the symbols in each pay line meeting set criteria. Gaming machines may now have five, six or more playing reels, and accordingly more possible pay lines per gaming cycle.

In the art, it is known to provide bonus features as a mechanism for awarding higher prizes such as jackpot prizes. The bonus feature can be the substitution or change of symbols to provide different symbol combinations corresponding to a higher payout. In other machines, the bonus feature is a secondary game.

Various technologies have investigated alteration of outcome probabilities and awards variations in bonus events.

EP 0 874 337 A1 , "Gaming Machine with Bonus Mode" published Oct. 10, 1998 describes a bonus game involving multiple plays presented for an underlying gaming machine such as a slot machine. A Bernoulli trial procedure is used to allow a player to repeatedly play a high odds bonus game (such as another slot game) and receive awards until a losing combination occurs (i.e., winning until losing). The hit rate in the bonus game is greater than 50% (preferably higher than 70%) which results in a much lower hit rate in the underlying game. This hit rate difference causes the player to endure the low hit rate of the underlying slot game in order to qualify for the high hit rate of the bonus game. The length of the bonus game is longer when the hit rate for the bonus game is higher. This bonus feature allows a player to win each bonus game and collect winnings until the player receives a losing combination (i.e., losing until winning). Other high odds and "win till you lose" bonus games are found in UK Patent Applications GB 2 180 087 and GB 2 084 371 A.

U.S. Patent No. 6,896,615 (Berman) describes a video gaming system with a bonus event. In one format of play, the gaming participant selects one or more symbols that will be played, in such an embodiment, the participant is afforded an opportunity to select which one or more symbols to play, in the hopes that a predetermined number of adjacent ones of the selected symbols will result. This selection may be accomplished via a user interface. One particular embodiment includes requiring increasing wager amounts for each symbol selected. For example, a first wager amount may be required if the user selects only one symbol, and an increased wager may be required for increased numbers of selected symbols.

U.S. Patent No. 6,328,468 (Walker et al.) discloses an electronic amusement device and a method for operating the device. In accordance with one embodiment, a slot machine receives an initiation signal to initiate game play at the slot machine. The slot machine conducts a game in response to the initiation signal. The slot machine determines whether a propagation criteria has been achieved and outputs a propagation signal, indicating a performance adjustment, to at least one other slot machine. In accordance with a second embodiment, a slot machine that stores a performance level is disclosed. The slot machine receives a propagation signal indicating a performance adjustment, and the slot machine adjusts the performance level accordingly. A slot server and method for operating the server are also disclosed.

US Patent No. 6,217,448 (Olsen) describes a method for providing bonus jackpot payoffs during a bonus mode time period in a system of linked gaming machines interconnected to a controller. Eligible gaming machines are determined at the time the bonus time period starts. Once the bonus mode time period starts, a portion of the eligible gaming machines are randomly selected for multiple jackpot bonus payoff opportunities. The random selection determines the rate the opportunities are issued and the average length of the bonus mode time period. Once gaming machines are selected they are allowed to complete the game they are currently involved in and should the play result in a winning combination, then the game payoff is multiplied by a bonus multiplier. The underlying gaming machine is responsible, in a conventional fashion, for paying the game payoff and the controller then authorizes a further jackpot bonus payoff of the bonus multiplier less one times the game payoff. The bonus pool value is then decremented by the amount paid by the controller. This process repeats until the bonus mode multiplier opportunities for each bonus multiplier in each bonus round is completed or until the bonus pool value drops below zero.

U.S. Patent No. 6,068,552 (Walker et al.) describes a gaming device such as a video based slot machine that provides a player the ability to modify at least one parameter of the slot machine. The slot machine then modifies other parameters to ensure a desired house advantage. Odds, payout schedules and wager amounts may be customized by a player, and the slot machine automatically determines changes in other parameters which were not customized to maintain a constant house advantage. Software running on the slot machine uses an equation that takes into account pertinent parameters or variables such as size of jackpot, amount wagered taken in at each puil, and probability of hitting the jackpot at each pull. Based on the equation, the software adjusts parameters other than the one(s) specified by the player so that the outcome (the house advantage) remains constant with each pull. A player interface provides an easy to use method of modifying selected parameters. US Patent No. 5,876,284 (Acres et al.) describes a method of operating gaming devices interconnected by a computer network to a host computer, that comprises: allowing play to occur on the gaming devices; paying to each device in accordance with a payout schedule after each game; sending a first reconfiguration command from the host computer to a gaming device over the network; receiving the first reconfiguration command at the gaming device; reconfiguring the gaming device responsive to the received first reconfiguration command, wherein the gaming device reconfigures its payout schedule in accordance with the received first reconfiguration command; allowing additional play to occur on the gaming devices; paying to the reconfigured device in accordance with the first payout schedule and a first bonus payout schedule after each game for so long as the gaming device remains reconfigured; sending a second reconfiguration command from the host computer to said gaming device over the network; receiving the second reconfiguration command at said gaming device; reconfiguring said gaming device responsive to the received second reconfiguration command, wherein the gaming device reconfigures its payout schedule in accordance with the received second reconfiguration command; allowing additional play to occur on the gaming devices; and paying to the reconfigured device in accordance with the first payout schedule and a second bonus payout schedule after each game for so long as the gaming device remains reconfigured.

U.S. Patent No. 5,580,309 (Piechowiak) describes a linked system that operates on a system of interconnected gaming machines and selectively provides one or more active features to all of the gaming machines linked to the system. The enablement of the feature may be based on the combined results from previous plays on the individual gaming machines. The feature may be a bonus award for a specific displayed combination, an increased possibility for a winning combination, or any other feature which alters the normal operation of the gaming machines. The first machine to generate a winning game result to which the feature applies will be given an award based upon the feature. The feature is then disabled and the system returns to normal play mode until the feature is again enabled. Various other features are described.

U.S. Patent No. 6,268,781 (Bennet) describes that it is normal for machines of the type having multiple pay lines available, that the player would purchase the option of playing for a win on lines other than the centre line. In order to add further player interest, the game is also provided with a random feature whereby under certain circumstances, a further combination of symbol positions, referred to as the "mystery line", will be randomly selected by the machine's controller to give the player another winning opportunity. A prize is paid to the player in the event that a predetermined combination of symbols is displayed in the randomly selected arrangement of symbol locations, "mystery line".

U.S. Patent No. 6,227,971 (Weiss) describes a gaming machine including reels that either move mechanically or are simulated via video. The indicia on the reels determines awards when the indicia on a pay line corresponds to that which is announced on the pay table. However, in addition, indicia on the reels includes directional vectors which have an effect on a thematically correlated "second" game. The second game has a different degree of "volatility" than the primary reel game where each indicium always changes on successive tries. Instead, the second game only changes as a function of vectors appearing on the primary game. Vectors preferably do not appear on all indicia of the pending game. Thus a player who plays successive games plays can win if a pay line of the secondary game remains constant or improves on the successive play. Thus, that aspect of the gaming device which appears less volatile rewards a player's successive plays by providing an award associated with this less volatile secondary game. As stated, the use of the vectors on the indicia of the primary reel portion of the game serves as directives for the second game. The less volatile secondary game is preferably optional; therefore a player needs to elect to partake in this secondary game, typically by making an additional wager. Assume that the player has made an additional wager, thereby enabling the features of the secondary game. The vector's appearance on the primary game will effect the secondary game by transferring the symbol associated with the vector (e.g., a cherry cluster) to a pay line of the secondary game. If no vector is present, the symbol on the secondary pay line from a previous game will not change. The significance of the existence or non-existence of vectors is that a player having a winning pay line on the secondary game from a prior game will again be awarded so long as the secondary winning outcome is undisturbed by a vector.

In respect of bonus features, it is desirable to provide a linear probability of achieving higher prizes related to the level of player wager. The attraction to gaming machine operators is that linear probability encourages players to increase their wagers per game. While linear probability related to player wagers has been implemented in prior art machines, the mathematical implementation is normally hidden within the internal processing of the game controller and is not readily perceived by the player during gameplay. As such, a player may not be convinced that the level of wager made has any real effect upon the chances of winning higher prizes. SUMMARY OF THE INVENTION

The technology described herein relates to bonus events based upon play in an underlying game. The bonus event comprises selection of symbols masking value events. The number of selectable symbols provided, the proportional number of value symbols provided to the number of selectable symbols provided, and/or the relative value of the value symbols can be varied with respect to the size of the initial wager on the underlying game event.

According to a first aspect of the present invention there is provided a method of operating a gaming machine, including at least the steps of: receiving a wager from a player for a primary game, the primary game being capable of producing a trigger event outcome; playing the primary game and awarding any winnings from the outcome of the primary game to the player; wherein, if the primary game outcome includes the trigger event outcome, providing a bonus feature, the bonus feature including the steps of: displaying a plurality of indicia, each indicium concealing a bonus prize; randomly selecting one or more of the indicia and revealing the respective concealed bonus prize(s); awarding the revealed bonus prize(s) to the player; wherein the number of indicia selected and revealed is dependent upon the size of the player's wager.

According to a second aspect of the present invention there is provided a method of operating a gaming machine, including at least the steps of: receiving a wager from a player for a primary game, said primary game being capable of producing a trigger event outcome; playing said primary game and awarding any winnings from the outcome of the primary game to the player; wherein, if said primary game outcome includes said trigger event outcome, providing a bonus feature, said bonus feature including the steps of: displaying a plurality of indicia, at least some indicia concealing a bonus prize; randomly selecting one or more of said indicia and revealing the respective concealed bonus prize(s); awarding the revealed bonus prize(s) to the player; wherein a) the number of indicia selected and revealed; b) the distribution and/or number of selectable indicia; c) the probability of prizes available in exposable indicia; and/or d) the value of exposable prizes, are varied with respect to the size of the player's wager.

Preferably, the primary game has an array of randomly arranged symbols, a number of the symbols having an additional symbol, wherein the trigger event outcome is defined by the occurrence of at least a predetermined number of additional symbols appearing on a wagered payline. The level of wager received on the wagered payline can determine the number of indicia selected and revealed.

The bonus prize can be a bonus credit amount, free spins, further bonus events, additional types of bonuses or a jackpot prize. Preferably, when a jackpot prize is revealed, a jackpot symbol is displayed. In exemplary embodiments more than one jackpot prize is available to be awarded and the method provides a random selection of which jackpot prize is to be awarded.

According to a further aspect of the present invention there is provided a gaming machine, including: a wager acceptor for receiving wagers from a player for a primary game; a display; and a game controller arranged to produce a primary game outcome and cause the display to display the primary game outcome and award any winnings from the outcome of the primary game to the player; wherein the primary game is capable of producing a trigger outcome which causes the controller to provide a bonus feature; and wherein, in the bonus feature, the controller causes the display to display a plurality of indicia, each or at least some of the indicia concealing a bonus prize, random selection of one or more of the indicia causes the display to reveal the respective concealed bonus prize(s) and the controller awards the revealed bonus prize(s) to the player; wherein the number of displayed indicia permitted to be selected and revealed, the proportional number of value symbols provided to the number of selectable symbols provided, and/or the relative value of the value symbols is dependent upon the size of the player's wager.

The terminology relating to "changing the proportional number of value symbols" reflects a format that can be described as follows. Although the preferred format of play of the bonus event may be that every indicia provided has a bonus award when revealed, it can add to the excitement, anxiety and expectation of the player to have some indicia that provide zero value, a joke, or even a small negative value when the indicia is removed to expose the "award" associated with that specific indicia. For example, it may be understood by the player that the bonus round for a wager of one credit or unit may be 10 indicia with three positive value awards available with the 10 indicia, a 30% proportion of the indicia having awards. With two units wagered, there may be an understanding that there will be 4 indicia with positive values, with 3 credits there would be 6 positive values available with the 10 indicia (60% proportion), with 4 credits there would be 7 or 8 positive value bonuses (70% or 80% proportion) and with a maximum of 5 credits there wouid be 10/10 or 100% positive responses or bonuses. Thus, the absolute number of indicia could remain the same, but the proportion of winning events would increase with increasing amounts of wagers. Similarly with increasing the relative value of wagers, it would be understood by the player that with a constant (or varying) number of indicia, the average bonus amount would be 2.2 credits for a single unit wager, 2.7 credits for a two unit wager, 3.2 credits for a three unit wager, 4.5 credits for a four unit wager and 6.0 for a five unit wager, or that the respective ranges of awards for bonus amounts would respectively be (by way of non-limiting examples) 1-10, 1- 20, 1-30, 1-40 and 1-75 for the wagers. These values or ranges would be advertised or otherwise disclosed on game play rules and payout tables. These increasing amounts and proportions and probabilities would also apply to multipliers and/or free spins if those were used as bonus awards.

The gaming machine may be part of a gaming system of linked machines. in which case, it is possible to provide a progressive jackpot as a potential bonus prize. BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention will now be described with reference to the accompanying drawings, in which: Fig. 1 is a schematic illustration of a prior art gaming machine display;

Fig. 2 is a flow chart of the operating steps in a preferred embodiment of the gaming machine;

Fig. 3 illustrates a screenshot of a primary game; Fig. 4 illustrates a screenshot upon initiation of a bonus feature; Fig. 5 illustrates a screenshot of the bonus feature having three prizes revealed.

DESCRIPTION OF PREFERRED EMBODIMENT The present invention will be described in detail with respect to several embodiments. It will however be understood that the present invention can be implemented in a many different ways, with the addition of further features and variations, as is known in the art of gaming machines. The present invention is applicable to stand alone machines, linked progressive machines and other linked jackpot arrangements, among other things.

Referring to Fig. 3, there is illustrated a display output 30 of a gaming machine in the form of an electronic simulated slot or poker machine. The machine includes five simulated independent and rotatable reels 31-35 which are disposed parallel with respect to each other. It will be appreciated that more or less reels can be employed in a machine in accordance with the present invention.

Each rotatable reel 31-35 includes a number of dispiayable faces, for example thirty, of which three are dispiayable at any one time. In alternative embodiments greater or fewer faces of each reel are dispiayable. Each face includes one symbol selected from a predetermined set of symbols. Ideally, the set of symbols will correspond to a common theme. In the example illustrated, the symbols correspond to the Atlantis mythology. It will be appreciated that any theme can be selected, for example, the symbols may represent the different faces of a deck of cards. A select number of faces include an additional symbol 36. This additional symbol 36 can be superimposed on the underlying symbol. Ideally, these additional symbols 36 are only provided on some of the reels. In the example illustrated, the additional symbols 36 appear only on reels 31 and 32. As will be explained in more detail below, the additional symbols 36 act to provide a trigger event which triggers the game controller to initiate a bonus feature.

A primary game is actuated by a player in a conventional way, by means of a button (not illustrated) such that the reels 31-35 are rotated either a predetermined or random number of times so that they come to rest and display three faces from each of the five reels 31-35. The resulting display displays fifteen symbols in a three by five array.

As with the prior art example illustrated in Fig. 1 , the display further provides an indication of the amount of total betting credits available to the player, the total amount of credits to be bet per gaming cycle of the gaming machine and a win meter indicative of payouts to the user in a previous gaming cycle. The display also shows the number of possible payline configurations beside the outermost reels. Furthermore, the display provides an indication of current jackpot levels, in the example illustrated there are twenty possible payiines. Before a player can actuate the primary game cycle, the player must first make a wager. There are two elements to the wager. Firstly, the player must select how many payiines they intend to wager upon and, secondly, the amount of wager per payline. In the present example, the player can wager between a minimum of one credit per payline up to a maximum of five credits per payline. The wagers can be entered by any suitable means, for example, touch screen buttons.

Referring to Fig. 2, once the player has selected and entered their wager the player can actuate the machine to commence the primary game 201. The reels 31-35 are rotated and come to rest to display the primary game outcome. As with conventional gaming machines, if the displayed outcome includes a predetermined combination of symbols appearing on a wagered payline then the player has won a standard win and the game controller awards the corresponding winnings to the player 202.

If in the primary game outcome, a predetermined number of additional symbols 36 appear on a wagered payline then the bonus feature is triggered 203. In the absence of a bonus feature trigger, the game cycle ends. In the illustrated example, where the additional symbols 36 appear only on the first two reels 31 , 32, only two additional symbols 36 need to appear on a wagered payline to trigger the bonus feature. It will be appreciated that the more payiines the player selects to place a wager upon, the greater the chance of achieving a trigger condition. Therefore, the player can readily perceive a correlation between their wager input and the chances of achieving a trigger condition. The triggered bonus feature is illustrated in Fig. 4. As shown, a number of indicia 40, in the form of top hats, are displayed to the player 204. The displayed indicia 40 can be superimposed upon the primary game display. Each indicium 40 may or does conceal a bonus prize, randomly selected by the game controller. Ideally, the distribution and/or number of selectable symbols and/or the probability of available exposable symbols and/or the value of exposable symbols can be varied with respect to the size of at least some of the bonus values. A preferred embodiment is where the number of indicia displayed corresponds with or at least respectively change (increase in number size or probability as the size of the initial wager increases) with the maximum number of credits that can be wagered per payline. A variety of bonus prizes are provided from which the game controller can randomly select, such as fixed bonus credit awards, free spins, free games or winning wager multipliers. Ideally, at least one potential bonus prize that can be selected by the game controller is a jackpot prize. The game controller determines the size of the player's wager on the payline which triggered the bonus feature 204. The amount of this wager dictates how many of the indicia 40 can be selected to reveal the corresponding concealed bonus prize. Ideally, this selection is automatically performed by the game controller 205. Therefore, in the present embodiment, if the player's wager on the trigger payline was only one credit then the controller will select and reveal the bonus prize concealed behind only one of the indicia 40. If, instead, the player wagered the maximum of five credits on the triggering payline then the game controller will reveal the bonus prizes concealed behind all five indicia 40. Referring to Fig. 5, the bonus feature is shown with three of the indicia revealing bonus prizes, two of which are fixed credit bonus amounts 44, that the game controller awards to the player 206, while the third is a jackpot symbol 46, indicating a jackpot win 207.

It will be appreciated that the larger the player's per line wager the more chance the player has of winning a jackpot. Therefore, the piayer can readily perceive a correlation between their wager input and the chances of achieving a jackpot win.

Ideally, the gaming machine may have more than one jackpot capable of being awarded. For example, the gaming machine may have a stand alone mini and major jackpot awards. In exemplary embodiments, the gaming machine is linked to a gaming system having a number of machines and one or more progressive jackpot pools. In the case of multiple potential jackpots, the system controller would randomly select one of the jackpots upon a jackpot symbol being revealed 208. In a linked system, the bonus game could be conveniently controlled by the central game controller, or alternatively controlled locally with communication to the central controller in the event that a progressive jackpot is won.

When all the applicable number of indicia has been revealed, the total winnings are awarded to the player and the gaming cycle ends 209.

In practice, it may be possible that the primary game outcome produces a trigger condition on more than one payline. In such a case, depending upon the paylines wagered upon by the player, the bonus feature can be repeated for each additional wagered triggering payiine before the game cycle ends. While the present invention has been described with respect to specific embodiments, it will be appreciated that various modifications and changes could be made without departing from the scope of the invention.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A method of operating a gaming machine, including at least the steps of: receiving a wager from a player for a primary game, said primary game being capable of producing a trigger event outcome; playing said primary game and awarding any winnings from the outcome of the primary game to the player; wherein, if said primary game outcome includes said trigger event outcome, providing a bonus feature, said bonus feature including the steps of: displaying a plurality of indicia, at least some indicia concealing a bonus prize; randomly selecting one or more of said indicia and revealing the respective concealed bonus prize(s); awarding the revealed bonus prize(s) to the player; wherein a) the number of indicia selected and revealed; b) the distribution and/or number of selectable indicia; c) the probability of prizes available in exposable indicia; and/or d) the value of exposable prizes, are varied with respect to the size of the player's wager.

2. A method of operating a gaming machine, including at least the steps of: receiving a wager from a player for a primary game, said primary game being capable of producing a trigger event outcome; playing said primary game and awarding any winnings from the outcome of the primary game to the player; wherein, if said primary game outcome includes said trigger event outcome, providing a bonus feature, said bonus feature including the steps of: displaying a plurality of indicia, each indicium concealing a bonus prize; randomly selecting one or more of said indicia and revealing the respective concealed bonus prize(s); awarding the revealed bonus prize(s) to the player; wherein the number of indicia selected and revealed is dependent upon the size of the player's wager.

3. The method according to claim 1 or 2, wherein said primary game has an array of randomly arranged symbols, a number of said symbols having an additional symbol, wherein said trigger event outcome is defined by the occurrence of at least a predetermined number of additional symbols appearing on a wagered payline.

4. The method according to claim 3, wherein the level of wager received on said wagered payline determines the number of indicia selected and revealed.

5. The method according to claim 3 or 4, wherein said array of randomly arranged symbols are displayed on a plurality of reels.

6. The method according to claim 5, wherein said additional symbols are provided on some, but not all, of said reels.

7. The method according to any one of the preceding claims, wherein the bonus prize is a bonus credit amount or a jackpot prize.

8. The method according to claim 7, wherein, when a jackpot prize is revealed, a jackpot symbol is displayed.

9. The method according to claim 8, wherein more than one jackpot prize is available to be awarded, the method further including the step of randomly selecting which jackpot prize is to be awarded.

10. The method according to claim 7, wherein at least one jackpot prize available to be awarded is a progressive jackpot.

11. A gaming machine, including: a wager acceptor for receiving wagers from a player for a primary game; a display; and a game controller arranged to produce a primary game outcome and cause said display to display said primary game outcome and award any winnings from the outcome of the primary game to the player, wherein said primary game is capable of producing a trigger outcome which causes said controller to provide a bonus feature; and wherein, in said bonus feature, said controller causes said display to display a plurality of indicia, at least some indicia concealing a bonus prize, random selection of one or more of said indicia causes the display to reveal the respective concealed bonus prize(s) and the controller awards the revealed bonus prize(s) to the player; wherein a) the number of displayed indicia permitted to be selected and revealed; b) the distribution and/or number of selectable indicia; c) the probability of prizes available in exposable indicia; and/or d) the value of exposable prizes, are varied with respect to the size of the player's wager.

12. A gaming machine, including: a wager acceptor for receiving wagers from a player for a primary game; a display; and a game controller arranged to produce a primary game outcome and cause said display to display said primary game outcome and award any winnings from the outcome of the primary game to the player, wherein said primary game is capable of producing a trigger outcome which causes said controller to provide a bonus feature; and wherein, in said bonus feature, said controller causes said display to display a plurality of indicia, each indicia concealing a bonus prize, random selection of one or more of said indicia causes the display to reveal the respective concealed bonus prize(s) and the controller awards the revealed bonus prize(s) to the player; wherein the number of displayed indicia permitted to be selected and revealed is dependent upon the size of the player's wager.

13. The gaming machine according to claim 11 or 12, wherein the controller automatically performs the random selection of one or more of said indicia.

14. The gaming machine according to any one of claims 11 to 13, wherein said primary game has an array of randomly arranged symbols, a number of said symbols having an additional symbol, wherein said trigger event outcome is defined by the occurrence of at least a predetermined number of additional symbols appearing on a wagered payline.

15. The gaming machine according to claim 14, wherein the level of wager received on said wagered payline determines the number of indicia selected and revealed.

16. The gaming machine according to claim 14 or 15, wherein said array of randomly arranged symbols are displayed on a plurality of reels.

17. The gaming machine according to claim 16, wherein said additional symbols are provided on some, but not all, of said reels.

18. The gaming machine according to any one of claims 11 to 17, wherein the bonus prize is a bonus credit amount or a jackpot prize.

19. The gaming machine according to claim 18, wherein, when a jackpot prize is revealed, a jackpot symbol is displayed.

20. The gaming machine according to claim 19, wherein more than one jackpot prize is available to be awarded, the controller randomly selects which jackpot prize is to be awarded upon the display of a jackpot symbol.

21. A gaming system including a plurality of linked gaming machines as claimed in any one of claims 11 to 20.

22. The gaming system according to claim 21 , wherein the bonus prize can be a progressive jackpot prize.