Electronic gaming machine and gaming method

An electronic gaming machine has an electronic game controller and a display where game symbols are arranged in an array of predetermined groups, at least one of the groups displaying at least one special symbol in a first play of the game and a subsequent play. In the first play, the electronic game controller selects a first group to display the at least one special symbol and in the subsequent play, the electronic game controller selects a different group to the first group to display the at least one special symbol. A gaming method is also provided.

BACKGROUND

The present invention relates to an electronic gaming machine and in a particular an electronic gaming machine using a base game and a feature game. The invention has been developed primarily for use as an electronic gaming machine and will be described hereinafter by reference to this application.

The following discussion of the prior art is intended to present the invention in an appropriate technical context and allow its advantages to be properly appreciated. Unless clearly indicated to the contrary, however, reference to any prior art in this specification should not be construed as an express or implied admission that such art is widely known or forms part of common general knowledge in the field.

Conventional gaming machines typically involve awarding prizes to a player according to predetermined combinations of game symbols that appear on an array of game squares displayed on a screen, typically organised into three rows and five columns (a 5×3 array). Other arrays, such as a 3×3 or 4×3, may be used. Each gaming machine randomly selects the game symbols that appear on the array, each column of the array being a “reel”.

In an electronic gaming machine, the mechanical reels are replaced with video images of the reels, which are displayed on a video display screen. The electronic gaming machine has an internal electronic game controller, typically a computer, that controls the display of images on the video display screen so that the reels are visibly spun on the screen to simulate a physical reel of a traditional gaming machine. Electronic gaming machines are also more versatile in presenting game information, varying the probabilities for a player to win a prize and varying the type of game that is played.

In an electronic gaming machine, the mechanical reels are replaced with video images of the reels, which are displayed on a video display screen. The electronic gaming machine has an internal electronic game controller, typically a computer, that controls the display of images on the video display screen so that the reels are visibly spun on the screen to simulate a physical reel of a traditional gaming machine. Electronic gaming machines are also more versatile in presenting game information, varying the probabilities for a player to win a prize and varying the type of game that is played.

Bonus or “feature” games may be provided by an electronic gaming machine in addition to the base or main game. Typically feature games use the same set of reels as the main game and are limited to a set of free games operated under a single set of rules. Once the free feature games have been played, the electronic gaming machine resets itself and returns the player back to the base game. This standard structure to game play limits the variation in the play of the electronic gaming machine. Consequently, it is difficult to retain player interest because there is no apparent incentive for the player to continue playing the same electronic gaming machine once the player becomes familiar with the feature game and the main game. Also, it is difficult to retain player interest since there is little differentiation between gaming machines in terms of the main and feature games that are played.

It is an object of the present invention to overcome or substantially ameliorate one or more of the disadvantages of prior art, or at least to provide a useful alternative.

It is an object of the invention in at least one preferred form to provide an electronic gaming machine and a method for controlling an electronic gaming machine that encourages player interest.

SUMMARY

According to a first aspect of the invention, there is provided an electronic gaming machine comprising:

a display for displaying game symbols for playing a game, where predetermined winning combinations of randomly selected game symbols award prizes to a player and said game symbols are arranged in an array of predetermined groups, and

an electronic game controller for controlling the display of game symbols on the display,

wherein said electronic gaming machine guarantees that at least one of said groups displays at least one special symbol in a first play of said game and a subsequent play of said game;

in said first play, said electronic game controller selects at least one first group to display said at least one special symbol, and

in said subsequent play, said electronic game controller selects at least one second group different to said at least one first group to display said at least one special symbol.

Preferably, said electronic gaming machine guarantees the selection of two or more first groups to display said at least one special symbol, wherein in said first play, said electronic game controller selects two or more first groups to display said at least one special symbol with said at least one first group, and in said subsequent play, said electronic game controller reselects at least one of said first groups to display said at least one special symbol with said at least one second group.

Preferably, said electronic game controller selects said first groups, reselects said at least one of said first groups and selects said at least one second group according to a predetermined order for said first play and said subsequent play. Alternatively, said electronic game controller randomly selects said first groups for said first play, and randomly reselects said at least one of said first groups and randomly selects said at least one second group for said subsequent play.

Preferably, said electronic game controller selects said at least one first group and said at least one second group according to a predetermined order for said first play and said subsequent play. Alternatively, said electronic game controller randomly selects said at least one first group and said at least one second group for said first play and said subsequent play.

Preferably, said electronic game controller reselects at least one of the selected groups from a preceding play of said game and further selects a new group that was not selected in said preceding play for each successive play of said game after said subsequent play. Alternatively, said electronic game controller reselects at least one of the selected groups from a preceding play of said game and selects a new group that was not selected in said preceding play for a predetermined number of successive plays of said game after said subsequent play.

Preferably, said first and said subsequent plays of said game are consecutive. Alternatively, said first and said subsequent plays are within a predetermined set of plays of said game.

Preferably, said electronic game controller guarantees said display of said at least one special symbol in response to a trigger event. Alternatively, said electronic game controller selects said selected groups in response to a trigger event.

Preferably, said electronic game controller randomly generates a number and determines whether said randomly generated number is a predetermined number or within a predetermined range of numbers. Alternatively, said trigger event comprises said electronic game controller randomly generating a number and determining whether said randomly generated number is a predetermined number or within a predetermined range of numbers. More preferably, said predetermined number or range of numbers corresponds to the number of selected groups for said first play. Where two or more first groups are selected to display said at least one special symbol for said first play, alternatively, said predetermined number is more than two and is equivalent to the number of selected first groups for said first play.

Preferably, said trigger event comprises the appearance of at least one trigger symbol. Preferably, the electronic game controller randomly determines the appearance of said trigger symbol. In another preferred form, said trigger event further comprises a different random event determined by said electronic game controller during play of said game.

Preferably, said game is a feature game of said electronic gaming machine. Alternatively, said game is a main or base game of said electronic gaming machine.

Where said game is a feature game, said electronic game controller also causes said display to display game symbols for playing a base game, wherein predetermined winning combinations of randomly selected game symbols results in the award of prizes to said player. Preferably, in response to said trigger event, said electronic game controller causes said display to display game symbols for playing said feature game.

Preferably, said trigger event further comprises the appearance of at least one trigger symbol during play of said base game. In one preferred form, said trigger event comprises the appearance of three trigger symbols during play of said base game. Preferably, the electronic game controller randomly determines the appearance of said trigger symbol(s). Alternatively, said trigger event further comprises a different random event determined by said electronic game controller during play of said base game.

Preferably, said electronic game controller awards a random number of plays of said game in response to the trigger event. Alternatively, the number of plays of said game awarded by said electronic game controller in response to the trigger event depends of the amount wagered by the player.

Preferably, said electronic game controller causes the display of said feature game and said base game during play of said base game, said feature game being inactive until triggered. In this preferred form, the change in said feature game from being inactive to active may be indicated on the display. Alternatively, said electronic game controller causes the display of said feature game in response to said trigger event.

Preferably, said electronic game controller causes the display of said base game on a separate display to said display. Alternatively, said electronic game controller causes the display of said feature game and said base game on the same display.

According to a second aspect of the invention, there is provided a gaming method for an electronic gaming machine comprising a display and an electronic game controller, the method comprising the steps of:

controllably displaying game symbols for playing a game, where predetermined winning combinations of randomly selected game symbols in said game results in the award of prizes to a player and said game symbols are arranged in an array of predetermined groups;

guaranteeing at least one of said groups displays at least one special symbol in a first play of said game and a subsequent play of said game;

selecting at least one first group to display at least one special symbol in said first play, and

in said subsequent play, selecting at least one second group different to said at least one first group to display said at least one special symbol.

Preferably, said guaranteeing step comprises guaranteeing the selection of two or more first groups to display said at least one special symbol, said method further comprising the steps of selecting in said first play two or more first groups to display said at least one special symbol, and reselecting in said subsequent play at least one of said first groups to display said at least one special symbol with said at least one second group.

Preferably, said selecting step of said first groups, said reselecting step of said at least one of said first groups and selecting step of said at least one second group are performed according to a predetermined order for said first play and said subsequent play. Alternatively, said selecting step of said first groups for said first play, and said reselecting step of said at least one of said first groups and selecting step of said at least one second group for said subsequent play are performed randomly.

Preferably, said selecting steps comprise selecting said at least one first group and said at least one second group according to a predetermined order for said first play and said subsequent play. Alternatively, said selecting steps comprise randomly selecting said at least one first group for said first play and said at least one second group for said subsequent play.

Preferably, said method further comprises the steps of reselecting at least one of said selected groups from a preceding play of said game and further selecting a new group that was not selected in said preceding play for each successive play of said game after said subsequent play. Alternatively, said method further comprises the steps of reselecting at least one of said selected groups from a preceding play of said game and further selecting a new group that was not selected in said preceding play for a predetermined number of successive plays of said game after said subsequent play.

Preferably, said guaranteeing step is performed in response to a trigger event. Alternatively, said selecting steps are performed in response to a trigger event.

Preferably, said method further comprises the step of randomly generating a number and determining whether said randomly generated number is a predetermined number or within a predetermined range of numbers. Alternatively, said trigger event comprises said electronic game controller randomly generating a number and determining whether said randomly generated number is a predetermined number or within a predetermined range of numbers. More preferably, said predetermined number or range of numbers corresponds to the number of said first groups selected for said first play.

Preferably, said method further comprises the step of consecutively performing said first play and said subsequent play. Alternatively, said method further comprises the step of performing said first play and said subsequent play within a predetermined set of plays of said game.

Preferably, said game is a feature game of said electronic gaming machine. Alternatively, said game is a main or base game of said electronic gaming machine. Where said game is a feature game, said method further comprises the step of causing said display to display game symbols for playing a base game, wherein predetermined winning combinations of randomly selected game symbols results in the award of prizes to said player.

Preferably, said method comprises the step of awarding a random number of plays of said game in response to the trigger event. Alternatively, the awarding step comprises awarding the number of plays of said game based on the amount wagered by the player.

Preferably, said displaying step comprises displaying said feature game and said base game during play of said base game, said feature game being inactive until triggered. In this preferred form, the change in said feature game from being inactive to active may be indicated on the display. Alternatively, said displaying step comprises displaying said feature game in response to said trigger event.

Preferably, said method further comprises displaying said base game on a separate display to said display. Alternatively, said method further comprises displaying said feature game and said base game on the same display.

In both aspects of the invention, it is preferred that each of said groups comprises one or more of said game symbols. More preferably each of said groups comprises one or more visible positions in said array, each visible position displaying one of said game symbols. In one preferred form, each of said groups comprises animated images to simulate the rotation of a mechanical reel. In another preferred form, each of said groups comprises a row or a column of visible positions on said array, each visible position displaying one of said game symbols. In one particularly preferred form, said group comprises a column of said array displaying at least three visible positions, said column being animated to simulate the rotation of a mechanical reel. In an alternative preferred form, at least two of said groups are arranged in a column of said array, with each of said groups comprising animated images to simulate the rotation of a mechanical reel.

Likewise in both aspects of the invention, preferably, said at least one special symbol comprises at least one of a replacement symbol, a wild card symbol, a scatter symbol, bonus prizes, collector symbols, a win multiplier, wild multipliers, bonus wilds, random wild symbols, progressive symbols, bonus credits and jackpot symbols.

Preferably, the same game symbols are used in said feature game and said base game. Alternatively, different game symbols or a mixture of the same and different game symbols are used in said feature game and said base game.

Preferably, said feature game has the same number of game symbols as said base game. Alternatively, said feature game and said base game have different numbers of game symbols.

Preferably, the game symbols in said feature game and said base game are organised or arranged in the same way. In another preferred form, the game symbols in said feature game and said base game are organised or arranged differently to each other.

Preferably, said game symbols in said base game are arranged in an array. More preferably, said game symbols in said feature game and said base game are arranged in arrays of the same shape or type. Alternatively, said game symbols in said feature game and said base game are arranged in differently shaped arrays. The shapes of said arrays are preferably rectangular, circular, triangular, oval, semi-circular or other non-rectangular shape.

The method also preferably has the preferred features of the first aspect of the invention not otherwise stated above, where applicable.

According to a third aspect of the invention, there is provided a computer system comprising a central processing unit configured for communication with an electronic gaming machine, wherein said computer system is configured to perform the method of the second aspect of the invention.

According to a fourth aspect of the invention, there is provided a computer program configured to perform the method of the second aspect of the invention.

According to a fifth aspect of the invention, there is provided a non-transitive carrier medium carrying computer executable code that, when executed on a central processing unit configured for communication with an electronic gaming machine, causes the central processing unit to perform the method of the second aspect of the invention.

DETAILED DESCRIPTION OF THE VARIOUS EMBODIMENTS

Referring toFIG. 1, an electronic gaming machine1according to a first embodiment of the invention includes a cabinet2, a console3and an internal electronic game controller4. The console3has various input devices including vending slots5for receiving monetary bets and a plurality of buttons6for actuation by a player. The electronic game controller4is generally in the form of a central processing unit, such as a computer, and is in electronic communication with a display7and various input devices on the console3, as best shown inFIG. 2. It is also appreciated that a person skilled in the art would readily understand the location and use of the electronic game controller4in the electronic gaming machine1.

The display7is used to display game symbols8for playing a base or main game9and a feature game10on the electronic gaming machine1, as best shown inFIGS. 3 and 5. A player inserts a monetary amount into the electronic gaming machine1and selects an initial bet to initiate play of the base game9. As best shown inFIG. 3, in the base game9, the game symbols8are arranged in an array of predetermined groups in the form five columns or “reels”11a,11b,11c,11d,11e. The reels11are also alongside each other to form three rows and each have three visible positions in the form of cells12that each displays a game symbol8. It will be appreciated by one skilled in the art that other arrays could be used, such as the industry standard 5×3 or 3×3, 4×3, 5×5, 4×4, etc. Also, arrays with uneven rows and/or columns may also be used in other embodiments.

The game symbols8typically include picture symbols, wild symbols, scatter symbols and card symbols. Predetermined winning combinations of randomly selected game symbols8in the base game9result in the award of prizes to the player. These predetermined combinations of game symbols are typically in the form of pay lines that have at least one cell12from each reel11.

The electronic game controller4controls the display of the game symbols8in the base game9. In response to a trigger event during play of the base game9, the electronic game controller4causes the feature game10to appear on the display7for play by the player, as best shown inFIGS. 5 to 8where corresponding features have been given the same reference numerals. In this embodiment, the feature game10comprises game symbols8that are also arranged in an array of predetermined groups in the form of five reels11, each having three cells12to display game symbols8. As in the base game9, the reels11of the feature game are alongside each other to form three rows. The game symbols8also typically include picture symbols, wild symbols, scatter symbols and card symbols that are the same as the game symbols in the base game9.

The feature game10comprises a predetermined number of free plays or spins of the reels11. That is, the reels11in the feature game10are spun without requiring the player to make a bet, unlike the base game9. In the feature game10, predetermined winning combinations of randomly selected game symbols8result in the award of prizes to the player. In this embodiment, the predetermined winning combinations of game symbols8can award the same prizes available in the base game9. Similarly, the electronic game controller4also controls the display of the game symbols8in the feature game10.

Operation of this embodiment of the invention will now be described in more detail with referenceFIGS. 3 to 8, where corresponding features have been given the same reference numerals. The player initially makes a bet using vending slots5initiate play of the base game9and the electronic game controller4causes the reels11to appear to visibly rotate or “spin”, and randomly display the game symbols8. The initial bet involves the player selecting the number of pay lines that are to be played. For example, the player can bet or wager 50 credits to play 10 pay lines or 200 credits to play the maximum number of 50 pay lines. Also, the player can make any additional side bets or ante-bets to access additional features in the base game, such as increasing the number of winning combinations in the base game.

After the reels11stop spinning, the controller4determines whether there are any predetermined winning combinations of the game symbols8appearing in any player-selected pay lines, such as a two of a kind, three of a kind, four of a kind or five of a kind. It will be appreciated that other winning combinations of game symbols8can also be provided. If there is a predetermined winning combination present in the base game9, the electronic gaming machine1enters a winning game state and awards a prize according to the displayed predetermined winning combination.

Where a predetermined trigger event occurs during play of the base game9, which in this embodiment is the appearance of three scatter symbols in the form of a decorative seascape symbols13(as best shown inFIG. 3), the electronic game controller4causes the display of a transition screen14, as best shown inFIG. 4.

The trigger event also comprises the electronic game controller4randomly generating a number and determining whether that number is a predetermined number or falls within a predetermined range of numbers. The predetermined number or predetermined range of number corresponds to the number of reels11that are selected by the electronic game controller4. For game play reasons the maximum number of reels that are selected will always be one less than the maximum number of available reels. For example, the electronic game controller4can generate a number between 1 and 100 and any number between 1 and 25 would mean only one reel11is selected, any number between 25 and 50 would mean that two reels are selected, any number between 51 and 75 would mean that three reels are selected and any number between 75 and 100 would mean that four reels are selected. This can be used for any range of randomly generated numbers and the individual ranges corresponding to the number of reels can also be adjusted so that there is a progressively lower probability as the number of selected reels increase. For example, the probability selecting four reels would be less than the probability of selecting one reel.

Alternatively, the electronic game controller4can randomly generate a number that is equivalent to the number of reels that are selected. For example, if the number is two, then the electronic game controller4selects two reels11to each display at least one special symbol in during play of the feature game10.

The transition screen14has two information panels15and16to display information about the feature game11to the player. Information panel15indicates to the player the number17of reels11that are guaranteed to display at least one special symbol in the form of a flower symbol18. Thus, the selected reels11are guaranteed to have at least one flower symbol18appear on the display7at the end of the spin or play. In this case, the information panel15indicates that three of the five reels11are guaranteed to have a flower symbol18. Information panel16indicates to the player the number of plays or spins of the feature game10that have been awarded to the player. In this case, 5 free spins have been awarded to the player.

After the transition screen14, the electronic game controller4causes the display of the feature game10on the display7, as best shown inFIGS. 5 to 8. The initial conclusion of a spin or play of the feature game10is illustrated inFIG. 5, where the electronic game controller4has selected reels11b,11dand11e(corresponding to reels2,4and5under the conventional numbering of reels) to display the flower symbol18according to a predetermined order as set out in table19, as best shown inFIG. 9and discussed in more detail below. In this embodiment, the flower symbol18occupies each visible position of the selected reels11b,11dand11e. However, it will be appreciated the special symbols18do not necessarily appear on each visible position or cell12of the selected reels11b,11d,11e, but can appear on any number of positions on each selected reel.

Also, the flower symbol18is a replacement symbol, meaning that the flower symbol changes into another game symbol8at the conclusion of a spin or play of the feature game10. The game symbols in this embodiment include playing card symbols8a, picture symbols8b, wild symbols and scatter symbols13. In this case, the flower symbol18has randomly changed to queen card symbols8a, as best shown inFIG. 6. The queen card symbols8aoccupy the same cells12that were previously occupied by the flower symbols18. After the conversion or change of the flower symbols18, the electronic game controller4determines whether there are any predetermined winning combinations of game symbols8on the display7. Hence, the increased number of queen card symbols8aincreases the chances of the player winning a prize and/or winning a prize of higher value than otherwise would be obtained by a conventional spin of the reels11in the feature game10. Thus, the guarantee of selected reels11that will display special symbols increases the player's excitement and enhances his or her interest in playing the electronic gaming machine1.

The next play of the feature game10is shown inFIG. 7, where corresponding features have been given the same reference numerals. The electronic game controller4has selected a different reel, being reel11c(corresponding to reel3under the conventional numbering of reels), to the previously selected reels to display the flower symbol17. The electronic game controller4has also reselected two of the previously selected reels11, being reels11band11e(corresponding to reels2and5under the conventional numbering of reels). New reel11cwas not selected in the preceding play shown inFIGS. 5 and 6. Again, in this embodiment, the flower symbol18appears in each visible position or cell12of each selected reel11b,11cand11e.

As with the preceding spin, the flower symbol18changes into another game symbol8, in this case, frog symbol8b. After the replacement of the flower symbols18, the electronic game controller4determines whether there are any predetermined winning combinations of game symbols8on the display7. The increased number of frog symbols8bincreases the chances of the player winning a prize and/or winning a prize of higher value than otherwise would be obtained by a conventional spin of the reels11in the feature game10.

It should be noted that the guaranteed appearance of the special symbol18on the selected reels11do not prevent the appearance of the special symbol on non-selected reels in any of the free spins of the feature game10. Since the electronic game controller4randomly determines the game symbols8that appear on the non-selected reels, the special symbol can appear on any non-selected reel. For example, as shown inFIG. 7, a flower symbol18is shown in the top position of reel11deven though this reel was not selected by the electronic game controller4as guaranteeing the appearance of a flower symbol. This additional flower symbol18also changes to the same game symbol, being a frog symbol8b, as the other flower symbols.

In successive spins of the feature game10, the electronic game controller4continues to select a new reel that was not selected in that preceding spin to display the flower symbols18, as well as reselecting one of the selected reels from the preceding play or spin of the feature game.

Once all the free spins have been played in the feature game10, the electronic game controller4returns the electronic gaming machine1to the base game9. The electronic gaming machine1will await the trigger event to occur in a play of the base game9before proceeding to the feature game10.

Referring toFIG. 9, table19shows the predetermined order in which the electronic game controller4selects the reels11a,11b,11c,11d,11ethat are guaranteed to display the special symbol(s)17in the feature game10. In the table19, column20lists the number of free spins that are randomly selected by the electronic game controller4, while columns21,22,23and24indicate the number of selected reels (1,2,3and4reels, respectively) that are randomly determined by the electronic game controller4. Each cell of the table19indicates which of the reels are selected by the electronic game controller4based on the criteria in columns20,21,22,23and24. For example, in the embodiment described inFIGS. 5 to 8, the electronic game controller4randomly determines that five free spins are given to the player and that three reels are selected or guaranteed. Based on these criteria, cell25of table19indicates that for the first spin, reels11b,11dand11e(corresponding to reels2,4and5under the conventional numbering of reels) are selected to display the flower symbols18. Cell26of table19indicates that for the second spin, reels11b,11cand11e(corresponding to reels2,3and5under the conventional numbering of reels) are selected to display the flower symbols18. Cell27of table19indicates that for the third spin, reels11a,11cand11e(corresponding to reels1,3and5under the conventional numbering of reels) are selected to display the flower symbols18. The fourth spin corresponds toFIGS. 5 and 6, and cell28of table19indicates that reels11b,11d,11e(corresponding to reels2,4and5under the conventional numbering of reels) are selected to display the flower symbols18. Finally, the fifth spin corresponds toFIGS. 7 and 8, and cell29of table19indicates that reels11b,11c,11e(corresponding to reels2,3and5under the conventional numbering of reels) are selected to display the flower symbol18.

It should also be noted from table19that the electronic game controller4may reselect more than one previously selected reel between successive spins of the feature game10. For example, in column24of table19, reels3and5are reselected for spins4to7, as indicated by cells30,31,32and33.

In one preferred form, the invention is implemented in a base game, rather than a feature game. In this preferred form, the base game would operate as described above in relation toFIGS. 5 to 8, but in this case initial and subsequent plays where the reels are selected, and reselected with a newly selected reel, integrate into the play of the base game9.

In another preferred form, the plays or spins need not be free as described in the preferred embodiment. Rather, the player may be required to make a further bet in order to play the spins in which the reels are selected and reselected with a new reel. Alternatively, where the invention is implemented in a base game9, the player makes a bet for each spin as in a conventional base game.

In a further preferred form, the groups take the form of single cell reels, each arranged into an array. In this further preferred form, the single cell reels spin independently of each other, even though they may the organised into an array having rows and columns. For example, three single cell reels may the organised to form a single column in an array. Likewise, fifteen single cell reels can be used to fill a standard 5×3 array, with five single cell reels in each column. Also, the groups may be multi-cell reels having cells less than or greater than the five-cell format found in standard reels.

The preferred embodiment has been described as reselecting at least one previously selected reel from the preceding spin and selecting a new reel that was not selected in the preceding spin for each successive spin in the feature game10. However, it will be appreciated that not each successive spin has to reselect one of the selected reels from the preceding spin, and instead the electronic game controller4can reselect at least one of the selected reels from a preceding play of said game and select a new column that was not selected in that preceding play for only a predetermined number of successive plays. For example, in another preferred embodiment, the electronic game controller4may reselect at least one selected reel and select a new reel for 5 successive free spins where 10 free spins have been awarded in the feature game. Also, the first spin and its subsequent spin in the feature game need not be consecutive, but instead the subsequent spin may occur later in the sequence of free spins. Furthermore, the “first” or initial spin in which the reels are selected to guarantee display of the special symbol(s) need not be the first spin of the feature game, but may occur as a later spin in the sequence of free spins in the feature game. For example, the initial or “first” spin illustrated inFIGS. 5 and 6can be a spin following the first play or spin of the feature game, such as the second or sixth spin in a sequence of 10 spins.

While the same game format is essentially used across the base game9and feature game10, it will be appreciated that the game format may vary across both games. For example, the base game9may be a wheel-type game or a four reel game and the feature game10may be standard five reel game. Similarly, the base game9and feature game10may each have different game symbols, game rules and pay tables that are unique to each game.

Also, in another preferred form, there is no need for a trigger event in the form of the appearance of a predetermined number of trigger symbols. Instead, the electronic game controller4can internally determine when to select reels that guarantee the appearance of special symbol(s). One way to implement this preferred form is for the electronic game controller4to internally generate a random number and checks if it is a predetermined number or within a predetermined range of numbers that will initiate selection of reels that guarantee the appearance of special symbol(s). For example, the predetermined range of numbers could be the range of numbers between 1 and 10 and the electronic game controller4internally generates a random number between 1 and 100. If the generated number is any one of numbers 1 to 10, then this results in the electronic game controller4displaying the feature game10with a suitable message to the player, such as the transition screen13, and then determines the number of reels11that are selected to show the special symbol18. Thus, the internal random number generation initiates both the feature game10and the number of reels11that are selected to show the special symbol18. Alternatively, the electronic game controller may perform two separate internal random number generations to determine initiation of the feature game10and the number of reels selected to display the special symbol18.

Other forms of special symbols18, beside replacement symbols, can include one or more of bonus prizes, collector symbols, a win multiplier, wild multipliers, bonus wilds, random wild symbols, progressives, bonus credits and jackpot symbols. Progressives operate in a similar manner to jackpot symbols in that a prize is awarded upon a certain number of progressive symbols are accumulated by the player over a number of games played on the gaming machine. It will be appreciated that the special symbol18is not limited to these game symbols and can include other game symbols.

While the embodiment of the invention has been described in relation to a base game and a feature game, it will be appreciated that the invention could include an additional feature game that is triggered by specific trigger symbols appearing in the feature game10. Also, the additional feature game may also have trigger symbols that trigger further feature game in a cascading fashion. These additional and further feature games could have the same game play elements as the feature game10or be different feature games entirely.

Also, in a further preferred form, the player can selectively stop spinning of the reels11in the feature game10to increase player interaction. Furthermore, the player can start spinning of the reels11in the feature game10to further enhance player interaction.

In other preferred forms, the base game9and feature game10are displayed on separate screens, rather than being sequentially replaced on a single screen7. Alternatively, the base game9and feature game10are displayed together on the screen7, with suitable animation or highlighting being used to indicate that the feature game10has become active.

In another preferred form, the video screen7is a touch screen for use in addition to the player-actuatable buttons6so as to enable the player to select various features, such as making monetary bets for the game and responding to any messages or requests issued on the electronic gaming machine1by the electronic game controller4. In this case, the player may control when the reels11start spinning and stop spinning in any of the base game9and feature game10by simply touching the relevant reel11.

It will be appreciated that while the preferred embodiments have been described in relation to an industry standard electronic gaming machine, the invention can be readily applied to other types of electronic gaming machines, including a personal computer (standing alone or connected to a communications network, LAN or WAN), mobile electronic devices (such as handheld or portable electronic devices) and other electronic devices capable of displaying a game. In the case of mobile electronic device, in one arrangement it may permit the player to make bets using “virtual” credits that represent a monetary value, but do not require the player to make a monetary transaction. Instead, the invention may provide a tiered access to the various features of the game so that the player can make relatively small payments to access particular features of the game or obtain additional benefits during game play. An alternative arrangement would require the player to purchase virtual credits or tokens via an interface on the mobile electronic device or an online interface accessible by the mobile electronic device. Similarly, either of the above described arrangements can be applied where the invention is implemented on a personal computer (PC) connected to the internet (wirelessly or not). In one example of the implementation, the PC would access an online casino over the internet to play the game of the invention or the game of the invention would be part of a social networking website. It is also contemplated that the player could also make regular payments to subscribe to continue playing the game on the mobile electronic device, PC or other electronic device.

In an alternative embodiment, the electronic gaming machine also provides an option for the player to play with either credits based on a monetary amount or virtual credits as discussed above. This can be implemented by way of a selection menu prior to playing the selected game or by providing a suitable menu button on screen during play of the selected game.

In another aspect, the invention includes a computer program configured to perform the invention. In this way the invention can be implemented in various ways on an electronic gaming machine. In a further aspect, the invention includes a computer system configured comprising a central processing unit configured for communication with an electronic gaming machine to perform the invention. In a yet another aspect, the invention includes a non-transitive carrier medium carrying computer executable code that, when executed on a central processing unit configured for communication with an electronic gaming machine, causes said central processing unit to perform the invention. In this case, the non-transitive carrier medium includes an external hard drive, a memory device, including a memory card, smart card, a radio frequency identification (RFID) device, USB key, magnetic card or other electronic storage device.

It will further be appreciated that any of the features in the preferred embodiments of the invention can be combined together and are not necessarily applied in isolation from each other. For example, the feature of providing a limited number of successive spins where reels are selected and reselected with a new reel in a larger set of free spins can be readily combined with the feature of including trigger symbols in the feature game to trigger additional feature games.

By making at least one reel guarantee the appearance of special symbols, with at least one of the guaranteed reel(s) changing between spins of the game, the invention increases player excitement and interest in the game, thus encouraging the player to continue playing the same electronic gaming machine. Furthermore, the reselection of a previously selected reel and selection of a new reel also enhances the player's anticipation between plays or spins of the feature game, as the player knows that a new reel will show special symbol(s) in addition to at least one previously selected reel. The invention thus provides a combination of predictable elements (the guarantee of special symbols on at least one reselected reel and a new reel) and unpredictable elements (which of the reels are reselected and newly selected) to provide a variety in game play not seen in convention electronic gaming machines. All these advantages of the invention result in the player being more likely to retain interest in continuing to play the same electronic gaming machine. Furthermore, since the electronic game controller controls operation of the base game and feature game, the invention can be readily implemented to existing gaming machines and other gaming systems. In all these respects, the invention represents a practical and commercially significant improvement over the prior art.