Patent Publication Number: US-2009233682-A1

Title: Gaming machine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims a priority from the U.S. Provisional Patent Application No. 61/035,586 filed on Mar. 11, 2008, the entire contents thereof are incorporated herein by reference for all purposes. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The gaming machine according to one or more aspects of the present invention relates to a gaming machine that displays variable symbols and stopped symbols. More particularly, it relates to a gaming machine which can award a high payout to a player even in a base game. 
     2. Description of Related Art 
     Conventionally, various gaming machines are installed in a gaming arcade or the like. These gaming machines include a type of a gaming machine that displays variable symbols and stopped symbols on a display thereof. 
     Players desire substantial awards from this type of gamine machine. To accommodate players&#39; requests for high payouts, the gaming machine awards a bonus game to the players if predetermined conditions are satisfied. A gaming machine is thus required that can yield a high payout even in a base game. 
     An object of the present invention is to provide a gaming machine capable of executing a game that has game characteristics which cannot be found in the above-described conventional art and capable of awarding a high payout to the players even in a base game. 
     SUMMARY 
     A gaming machine related to one or more aspects of present invention has a display and a processor. The processor accepts a bet of game value placed by a player. Upon accepting the bet of the game value, the processor executes the first lottery to determine a plurality of symbols that will be stopped on the display. If a winning combination corresponding to the first symbol is established with the results of the first lottery, the processor determines whether or not to change the first symbol stopped on the display to the second symbol with the second lottery. The processor starts variable display of the symbols. And then, the processor stops the plurality of the symbols on the display based on the result of the first lottery. The processor changes the first symbol stopped on the display to the second symbol based on the result of the second lottery. If the plurality of the symbols that have been stopped on the display constitute the predetermined winning combination, the player is awarded a prize corresponding to the winning combination. Specifically, if the first symbol stopped on the display is changed to the second symbol, the player is awarded a high payout based on the winning combination corresponding to the second symbol. As a result, this gaming machine can possibly meet expectation of players who seek high payouts even in the base game. This gaming machine can thus provide a game having new game characteristics which are not present in conventional art. 
     A gaming machine related to one or more aspects of present invention has a display and a processor. The processor accepts a bet of a game value placed by a player. Upon accepting the bet of the game value, the processor executes the first lottery to determine a plurality of the symbols that will be stopped on the symbol display area. If the winning combination corresponding to the first symbol is established with the result of the first lottery, the processor determines whether or not to change the first symbol stopped on the symbol display area to a second symbol with the second lottery. The processor displays a first background image on the background display area. At the same time, the processor starts variable display of the symbols. And then, the processor stops the plurality of the symbols on the symbol display area based on the result of the first lottery. Here, if it is determined to change the first symbol to the second symbol with the result of the second lottery, the processor changes the first background image displayed on the background display area to the second background image. After that, the processor changes the first symbol stopped on the display to the second symbol with the result of the second lottery. Specifically, after changing the display contents of the background display area from the first background image to the second background image, the gaming machine changes the first symbol in the symbol display area into the second symbol. Then, if a plurality of symbols which have been stopped on the symbol display area constitute a winning combination, the player is awarded a prize (for instance, a payout) corresponding to this winning combination. Thus, if the first symbol which has been stopped on the display is changed into the second symbol, the player is awarded a high payout based on the winning combination corresponding to the second symbol. As a result, this gaming machine can possibly meet expectation of players who seek high payouts even in the base game. After changing the display contents of the background display area, the gaming machine changes the first symbol. Accordingly, the gaming machine can enhance the sense of anticipation of the players with respect to a high payout. 
     A gaming machine related to one or more aspects of present invention has a display and a processor. The processor accepts a bet of a game value placed by a player. Upon accepting the bet of the game value, the processor executes the first lottery to determine a plurality of the symbols that will be stopped on the symbol display area by a first lottery. If the winning combination corresponding to the first symbol is established with the result of the first lottery, the processor determines whether or not to change the first symbol stopped on the symbol display area to the second symbol. Further, if it is determined to change the first symbol to the second symbol with the second lottery, the processor executes a third lottery with respect to a timing of the changing the first background image displayed on the background display area to the second background image. The processor determines the timing to be any of a start timing for variable display of symbols on the symbol display area, and a timing for display of stopped symbols on the symbol display area, based on the result of the third lottery. Here, when the game starts, the processor displays the first background image on the background display area. The processor changes the first background image displayed on the first background image to the second background image at a determined timing based on the result of the third lottery. As a result, this gaming machine can diversify the timing of display contents change on the background display area. And, this gaming machine can enhance the sense of anticipation of the players with respect to a high payout. The processor starts variable display of the symbol on the symbol display area. And then, the processor stops variable display of the symbol on the symbol display area based on the result of the first lottery. After that, the processor changes the first symbol stopped on the display to the second symbol based on the result of the second lottery. Specifically, after changing the display contents on the background display area from the first background image to the second background image, the gaming machine changes the first symbol of the symbol display area to the second symbol. Then, if the plurality of symbols that were stopped on the symbol display area constitute a winning combination, the player is awarded a prize (for instance, a payout) corresponding to the winning combination. Thus, if the first symbol which has been stopped on the display is changed into the second symbol, the player is awarded a high payout based on the winning combination corresponding to the second symbol. As a result, this gaming machine can possibly meet expectation of players who seek high payouts even in the base game. After changing the display contents of the background display area, the gaming machine changes the first symbol. Accordingly, the gaming machine can enhance the sense of anticipation of the players with respect to a high payout. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an explanatory diagram showing one example of an image effect in a slot machine according to one embodiment of the present invention; 
         FIG. 2  is a perspective view showing an outer appearance of a slot machine according to one embodiment of the present invention; 
         FIG. 3  is an explanatory diagram showing a configuration of a main display portion in the slot machine; 
         FIG. 4  is an explanatory diagram showing a configuration of a variable display portion in the main display area; 
         FIG. 5  is a block diagram showing a control system of the slot machine; 
         FIG. 6  is a block diagram showing a configuration of a sub-control board; 
         FIG. 7  is an explanatory diagram showing symbols that constitute one reel; 
         FIG. 8  is an explanatory diagram showing relationships between “HUMAN” symbols and “WEREWOLF” symbols; 
         FIG. 9  is an explanatory diagram showing one example of a symbol row constituting a reel; 
         FIG. 10  is an explanatory diagram showing a variable display portion in which symbols are variably displayed; 
         FIG. 11  is an explanatory diagram showing a variable display portion in which symbols are stopped; 
         FIG. 12  is an explanatory diagram showing a payout table for the slot machine; 
         FIG. 13  is a flow chart of a main control program in the slot machine; 
         FIG. 14  is a flow chart of the main game process program in the slot machine; 
         FIG. 15  is an explanatory diagram showing a table including associations between code numbers and symbols; 
         FIG. 16  is an explanatory diagram showing a table including associations between random number values and code numbers; 
         FIG. 17  is a flow chart of a symbol change lottery process program; 
         FIG. 18  is an explanatory diagram showing one example of a display content lottery table; 
         FIG. 19  is an explanatory diagram showing one example of an effect timing determination table; 
         FIG. 20  is a flow chart of a game result display process program; 
         FIG. 21  is an explanatory diagram showing one display example on the variable display portion prior to a specific symbol display change process; and 
         FIG. 22  is an explanatory diagram showing one display example on the variable display portion following the specific symbol display change process. 
     
    
    
     DETAILED DESCRIPTION 
     The various aspects summarized previously may be embodied in various forms. The following description shows by way of illustration of various combinations and configurations in which the aspects may be practiced. It is understood that the described aspects and/or embodiments are merely examples, and that other aspects and/or embodiments may be utilized and structural and functional modifications may be made, without departing from the scope of the present disclosure. 
     It is noted that various connections are set forth between items in the following description. It is noted that these connections in general and, unless specified otherwise, may be direct or indirect and that this specification is not intended to be limiting in this respect. 
     A gaming machine, a server, and a game system according to one or more aspects of the invention will be described in detail with reference to the drawings based on an embodiment embodying one or more aspects of the invention. However, it is appreciated that one or more aspects of the present invention may be embodied in distributable (via CD and the like) or downloadable software games, console games, and the like. In this regard, the slot machine may be a virtual slot machine that is displayed on a multi-purpose computer and/or dedicated kiosk. Aspects of the invention are described by way of hardware elements. However, it is appreciated that these elements may also be software modules that are executable in a computer. The software modules may be stored on a computer readable medium, including but not limited to a USB drive, CD, DVD, computer-readable memory, tape, diskette, floppy disk, and the like. For instance, aspects of the invention may be embodied in a JAVA-based application or the like that runs in a processor or processors. Further, the terms “CPU”, “processor”, and “controller” are inclusive by nature, including at least one of hardware, software, or firmware. These terms may include a portion of a processing unit in a computer (for instance, in multiple core processing units), multiple cores, a functional processor (as running virtually on at least one of processor or server, which may be local or remote). Further, in network-based gaming systems, the processor may include only a local processor, only a remote server, or a combination of a local processor and a remote server. 
     It is contemplated that one or more aspects of the invention may be implemented as computer executable instructions on a computer readable medium such as a non-volatile memory, a magnetic or optical disc. Further, one or more aspects of the invention may be implemented with a carrier signal in the form of, for instance, an audio-frequency, radio-frequency, or optical carrier wave. 
     Next, a detailed description will be given on embodiments relating to a gaming machine according to the present invention as applied to a slot machine  1 , while referring to the accompanying drawings. 
     As shown in  FIG. 2 , a slot machine  1  according to the present embodiment has an image display device such as a liquid crystal display or the like. The slot machine  1  advances a game by displaying images of various types of symbols on the image display device. In other words, slot machine  1  is a so-called video slot machine. 
     In the slot machine  1  according to the present embodiment, twelve types of symbols are variably displayed and are stopped on the variable display portion  3 D. The twelve types of symbols are constituted of “MOON” symbol  45 A through “ACE” symbol  45 L as will be described later. The contents of the prize to be awarded to the player are determined in accordance with the number of identical symbols that are stopped on the variable display portion  3 D. 
     Here, if a predetermined condition is satisfied, the slot machine  1  according to the present embodiment changes the “HUMAN” symbol  45 B which has been stopped on the variable display portion  3 D to a “WEREWOLF” symbol  50  (refer to  FIG. 1 ). This “WEREWOLF” symbol  50  is associated with the highest payout (refer to  FIG. 12 ). The contents of the prize to be awarded to the players are determined based on the type of the symbols that are stopped on the variable display portion  3 D. Accordingly, if the symbols are changed to the “WEREWOLF” symbol  50 , the player can be awarded the highest payout. As a result, the gaming machine  1  can enhance the sense of anticipation of the players with respect to a high payout. 
     If the “HUMAN” symbol  45 B which is stopped on the variable display portion  3 D changes to the “WEREWOLF” symbol  50 , the slot machine  1  changes the display state of a background display portion  3 E prior to change of the above symbol (refer to  FIG. 1 ). As a result, the slot machine  1  can enhance the sense of anticipation of a player with respect to change of a symbol into the “WEREWOLF” symbol  50 . 
     Next, the schematic configuration of the slot machine  1  according to the present embodiment will now be described in detail while referring to the accompanying drawings.  FIG. 2  is a perspective diagram showing an outer appearance of the slot machine  1  according to the present embodiment. 
     The slot machine  1  according to the present embodiment is an upright-type slot machine which is installed in a gaming arcade such as a casino or the like. The outer aspect of the slot machine  1  as shown in  FIG. 2  represents simply one example of the present embodiment. However, this outer aspect is not limited to this instance alone. 
     As shown in  FIG. 2 , the slot machine  1  has a cabinet  2 . The cabinet  2  is a housing portion that houses electrical or mechanical components. These electrical or mechanical components are used in execution of a predetermined game aspect. 
     The slot machine  1  has an upper display portion  3 A, a main display area  3 B and a lower display portion  3 C provided at a front face of cabinet  2 . The upper display portion  3 A, the main display area  3 B and the lower display portion  3 C display various types of game information. 
     The upper display portion  3 A is constituted of a liquid crystal panel and is arranged at an upper level of the cabinet  2 . The upper display portion  3 A displays effect images, payout tables for the game and game rules, etc. 
     The main display area  3 B is constituted of a liquid crystal panel which is arranged at a mid level of the cabinet  2 . The main display area  3 B has a variable display portion  3 D and a background display portion  3 E. 
     The variable display portion  3 D has five reel display portions  101  through  105  (refer to  FIG. 3 ). The symbol row is variably displayed and is stopped on the reel display portions. The reel display portions  101  through  105  each have three symbol display areas, respectively. More specifically, the reel display portions  101  through  105  each have symbol display areas  111 A through  111 C,  112 A through  112 C,  113 A through  113 C,  114 A through  114 C and  115 A through  115 C (refer to  FIG. 4 ). Each symbol display area is adapted to display one symbol, respectively (refer to  FIG. 11 ). In other words, fifteen symbols are displayed in a 3×5 matrix on the variable display portion  3 D. The number of reels and the number of symbols displayed in one reel display portion may vary. 
     The background display portion  3 E is constituted of portions other than the variable display portion  3 D of the main display area  3 B. Various background images are displayed on the background display portion  3 E. The background images which are displayed on the background display portion  3 E include a normal background image  90  and a special background image  95  as will be described later. Image effects by displaying animations and the like are carried out on the background display portion  3 E in accordance with the progress of the game in the slot machine  1 . 
     The main display area  3 B has a touch panel  4  provided at a front face of its liquid crystal panel. The player can thus enter various types of commands by operating the touch panel  4 . A payout amount display portion  5  and a credit amount display portion  6  are provided at a right lower portion of the main display area  3 B. The display position in the payout amount display portion  5  and the credit amount display portion  6  are random. A bet amount display portion for displaying the bet amount can also be provided in the main display area  3 B. The payout amount display portion  5  displays a payout amount to be awarded to the player. The credit amount display portion  6  displays the amount of credits that the current player possesses. 
     The lower display portion  3 C is constituted of a liquid crystal panel. The lower display portion  3 C is arranged at a lower level of the cabinet. The number of points recorded in the card and the number of game points are displayed on the lower display portion  3 C. When the card has not been inserted or when a card read failure has occurred, a corresponding message is displayed on the lower display portion  3 C. 
     A card reading portion  19  is provided at the periphery of the lower display portion  3 C. The card reading portion  19  reads the information stored in the card that the player possesses. 
     As was described above, in the present embodiment, the upper display portion  3 A, the main display area  3 B and the lower display portion  3 C are not limited to a liquid crystal display configuration. For instance, the respective display portions can be constituted using a CRT display, a plasma display, an LED display or other known display devices. 
     A lower panel  7  is provided at a lower side of the lower display portion  3 C. This lower panel  7  is constituted of a plastic panel and is illuminated by a back light. The lower panel  7  includes a picture of a character relating to the slot machine  1 , the name of the slot machine and the like. The lower panel  7  can be constituted of a liquid crystal display, a CRT display, a plasma display, an LED display or other known display devices. 
     An operation table  8  is provided at a lower side of the main display area  3 B. The operation table  8  has various types of operation buttons  26  (for instance, an exchange button, a CASHOUT button, a help button, a BET button and a start button and the like). The operation table  8  has a coin insertion portion  17  and a bill insertion portion  18 . 
     The position where the respective types of operation buttons are provided is random. As necessary, one portion of the respective operation buttons may be eliminated or buttons may be newly added or replaced. 
     A coin payout portion and a coin reception portion  21  are formed at a lower side of the cabinet  2 . The coin payout portion serves to payout coins when the exchange button or the CASHOUT button is operated. The coin reception portion  21  serves to receive coins that were paid out from the coin payout portion. The coin payout portion has a coin detecting portion provided therein. The coin detecting portion is constituted of a sensor or the like, and is adapted to detect the number of coins to be paid out from the coin payout portion. 
     A light emitting portion  25  is provided at the periphery of the cabinet  2  in the slot machine  1 . This light emitting portion  25  illuminates in a predetermined illumination pattern in the event of a winning combination or during the bonus game. Further, a speaker  34  for audio output is provided at a side face of the cabinet. The position where the light emitting portion  25  and the speaker  34  are provided is random. 
     As shown in  FIG. 2 , the slot machine  1  has a topper effect device  27  at the upper side of the cabinet  2 . The topper effect device  27  has a rectangular board shape and is arranged so as to be substantially parallel with the upper display portion  3 A. Various types of information are displayed on the topper effect device  27 . The shape of the topper effect device  27  is random. 
     Next, the internal configuration of the slot machine  1  will be described while referring to the drawings.  FIG. 5  is a block diagram showing an internal configuration of the entire slot machine  1 . As shown in  FIG. 5 , the slot machine  1  has a plurality of constituting elements and, as functional core, a main control board  71  including a controller  41 . The main control board  71  has a controller  41 , a random number generation circuit  45 , a sampling circuit  46 , a clock pulse generation circuit  47 , a divider  48 , an illumination effect driving circuit  61 , a hopper driving circuit  63 , a payout completion signal circuit  65  and a display portion driving circuit  67 . 
     The controller  41  has a main CPU  42 , a RAM  43  and a ROM  44 . The main CPU  42  operates in accordance with the programs stored in the ROM  44  and performs signal input and output with respect to the other constituting elements through the I/O port  49 . That is to say, the main CPU  42  executes the overall control of the slot machine  1 . The RAM  43  stores data and programs to be used when the main CPU  42  is operating. For instance, the RAM  43  temporarily retains the random number values which have been sampled by the sampling circuit  46 . The RAM  43  stores code numbers corresponding to the respective reel display portions  101  through  105 . The ROM  44  stores various types of control programs that will be executed by the main CPU  42  and permanent data. 
     The programs stored in the ROM  44  include game programs and game system programs (hereinafter referred to as game programs or the like). Further, the game programs include lottery programs. 
     The lottery programs are executed upon determining the code numbers corresponding to symbols which are stopped at a central position (specifically, symbol display areas  111 B,  112 B,  113 B,  114 B and  115 B) in the respective reel display portions  101  through  105  of the variable display portion  3 D. 
     This lottery program includes symbol weighing data. The symbol weighing data shows correspondence relationships between the respective code numbers and one or a plurality of random number values within a predetermined number value range (for instance 0 through 255). The probability of lottery with respect to each symbol on the real band is set by associating one or a plurality of random number values to one code number. By drawing the random number values in the lottery, symbols are finally identified from the random number values and are displayed in predetermined areas on the variable display portion  3 D. 
     The random number generation circuit  45  operates in accordance with the commands from the main CPU  42  and generates random numbers within a predetermined range. The sampling circuit  46  draws an arbitrary random number from the random numbers generated by the random number generation circuit  45 , in response to a command from the main CPU  42 . The sampling circuit  46  inputs the random number thus drawn to the main CPU  42 . The clock pulse generation circuit  47  generates a reference clock for causing the main CPU  42  to operate. The divider  48  inputs a signal obtained by dividing the reference clock by a constant cycle to the main CPU  42 . 
     The main control board  71  is connected to the touch panel  4 . As was described above, the touch panel  4  is arranged at a front face of the main display portion  3 B and is adapted to identify a coordinate position of the portion that was touched by the player. Specifically, the touch panel  4  can discriminate the operation of the player (for instance, the portion that the player has touched, and in what direction the touched portion has moved) based on the coordinate position information that was identified. A signal in accordance with the above discrimination is then inputted to the main CPU  42  through the I/O port  49 . 
     The main control board  71  is connected to the operation button  26  (the above-described start button, etc.) through the operation switch. Accordingly, a signal in accordance with a depression operation of the operation button  26  is inputted to the main CPU  42  through the I/O port  49 . 
     The illumination effect driving circuit  61  outputs an effect signal in accordance with a command from the main CPU  42 . The light emitting portion  25  and the topper effect device  27  perform illumination effects based on this effect signal. The topper effect device  27  is connected to the illumination effect driving circuit  61  through the light emitting portion  25 . 
     The hopper driving circuit  63  drives the hopper  64  under the control of the main CPU  42 . As a result, the hopper  64  carries out a predetermined operation to payout coins to the coin payout portion. The coin detecting portion  24  detects the number of coins that were paid out by the hopper  64  and then inputs coin amount value data showing the amount of coins that was detected to the payout completion signal circuit  65 . The payout completion signal circuit  65  receives coin amount value data from the coin detecting portion  24 . Then, when the received coin amount data has reached the set coin amount value, the payout completion signal circuit  65  inputs a signal that notifies completion of coin payout to the main CPU  42 . The display portion driving circuit  67  controls the display operation of the respective display portions including the payout amount display portion  5  and the credit amount display portion  6  and the like. 
     The main control board  71  is connected to the sub-control board  72 . As shown in  FIG. 6 , the sub-control board  72  carries out display control of the respective display portions and output control of the audio outputted by the speaker  34  based on the commands inputted from the main control board  71 . This sub-control board  72  is constituted on a separate circuit board from the circuit board that constitutes the main control board  71 . The sub-control board  72  has a micro computer (hereinafter referred to as “sub-micro computer  73 ”) which is provided as a main constituting element. Then, the sub-control board  72  has a sound source IC  78 , a power amplifier  79  and an image control circuit  81 . The sound source IC  78  controls the audio which is outputted from the speaker  34 . The power amplifier  79  functions as an amplifier with respect to the audio outputted from the speaker  34 . The image control circuit  81  operates as a display control section for the upper display portion  3 A and the main display area  3 B. 
     The sub-micro computer  73  has a sub-CPU  74 , a program ROM  75 , a work RAM  76  and I/O ports  77  and  80 . The sub-CPU  74  carries out a control operation in accordance with a control instruction transmitted from the main control board  71 . The program ROM  75  stores a control program executed by the sub-CPU  74 . The work RAM  76  is constituted as a temporary memory to be used in executing the control program in the sub CPU  74 . The sub-control board  72  does not have a clock pulse generation circuit, a divider, a random number generator and a sampling circuit, and executes random number sampling based on an operation program of the sub CPU  74 . 
     The image control circuit  81  has an image control CPU  82 , an image control work RAM  83 , an image control program ROM  84 , an image ROM  86 , a video RAM  87  and an image control IC  88 . The image control CPU  82  determines the image to be displayed on the upper display portion  3 A and the main display area  3 B based on the parameters set in the sub-micro computer  73  and the image control programs to be described later. 
     For instance, the image control CPU  82  displays a payout table and a help window on the upper display portion  3 A. The image control CPU  82  variably displays and stops symbols on the respective symbol display areas  111 A through  111 C,  112 A through  112 C,  113 A through  113 C,  114 A through  114 C and  115 A through  115 C in the variable display portion  3 D. When a predetermined condition is satisfied, the image control CPU  82  changes the “HUMAN” symbol  45 B to the “WEREWOLF” symbol  50 . The image control CPU  82  displays various background images (normal background image  90  and special background image  95 ) on the background display portion  3 E. 
     The image control program ROM  84  stores an image control program and various types of selection tables relating to display on the upper display portion  3 A and the main display area  3 B. The image control work RAM  83  functions as a temporary memory to be used in execution of the image control program in the image control CPU  82 . 
     The image control IC  88  forms an image in accordance with the contents determined by the image control CPU  82  and then outputs the image thus formed to the upper display portion  3 A and the main display area  3 B. The image ROM  86  stores dot data for forming an image. The video RAM  87  functions as a temporary storing section to be used when an image is formed by the image control IC  88 . 
     The internal configuration of the above-described slot machine  1  represents simply one example thereof and is not limited to the above-described configuration. For instance, the memory card and the PLD (Programmable Logic Device) can be constituted so as to be detachable. The memory card and the PLD can be constituted so as to allow readout of necessary information therefrom. 
     The slot machine  1  employs coins, bills or electronic valuable information (credits) corresponding to coins or bills, as gaming values. The gaming values applicable to this invention are not limited to these types. The gaming values can also be constructed so as to allow usage of medals, tokens, electronic money, tickets and the like, for instance. 
     Next, the symbols which are drawn on the reel band and are variably displayed on the reel display portion will now be described in detail while referring to the accompanying drawings.  FIG. 7  is a view showing symbols which are drawn on the reel band that is variably displayed on the reel display portions  101  through  105 .  FIG. 9  shows a reel band (exterior reel) which is variably displayed on each reel display portion. 
     As shown in  FIG. 7  and  FIG. 9 , the reel band according to the present embodiment includes twelve types of symbols. These twelve types of normal symbols are constituted of a “MOON” symbol  45 A (MOON), a “HUMAN” symbol  45 B (HUMAN), a “TREASURE” symbol  45 C (TREASURE), a “MEAT” symbol  45 D (MEAT), a “PLUM” symbol  45 E (PLUM), an “APPLE” symbol  45 F (APPLE), a “9” symbol  45 G ( 9 ), a “10” symbol  45 H ( 10 ), a “JACK” symbol  45 I (J), a “QUEEN” symbol  45 J (Q), a “KING” symbol  45 K (K) and an “ACE” symbol  45 L (A). 
     As shown in  FIG. 9 , the reel band includes twelve types of symbols (refer to  FIG. 7 ) arranged in a predetermined sequence. This reel band shown in  FIG. 9  represents merely one example thereof and the sequence in which the symbols are arranged is random. The number of symbols drawn on one reel band is random. In addition, the type of the symbols that were drawn is also random. 
     As shown in  FIG. 8  or the like, if a predetermined condition is satisfied, the “HUMAN” symbol  45 B is changed to the “WEREWOLF” symbol  50 . This predetermined condition means that a payout is made based on the “HUMAN” symbol  45 B and an award is won in the symbol change lottery process (S 15 ) that will be described later. The case in which the payout is made based on the “HUMAN” symbol  45 B corresponds to the case in which “HUMAN” symbols  45 B of a predetermined number or more are stopped on the variable display portion  3 D. In the present embodiment, this case is referred to as “special winning combination”. 
     In the present embodiment, changing of the “HUMAN” symbol  45 B which is stopped and displayed into the “WEREWOLF” symbol  50  is hereby referred to as “symbol change”. Specifically, “the case that a symbol change is made” shows “the case that the “HUMAN” symbol 45B which was stopped and displayed is changed into the “WEREWOLF” symbol 50”. Alternatively, “the case that no symbol change is made” shows “the case that the “HUMAN” symbol 45B which was stopped and displayed is stopped and displayed as is”. 
     Next, a game which is carried out in the slot machine  1  will now be described. In the game which is carried out in the slot machine  1  of the present embodiment, all the symbols are scatter symbols. Specifically, in the game according to the present embodiment, a prize is awarded based on the number of identical symbols displayed on the symbol display areas  111 A through  111 C,  112 A through  112 C,  113 A through  113 C,  114 A through  114 C and  115 A through  115 C in a 3×5 matrix in the variable display portion  3 D (refer to  FIG. 12 ). 
     To start a game in the slot machine  1 , the player operates the BET button to set the amount of bets and then depresses the start button. As a result, the reel band of each reel display portion  101  through  105  starts spinning. In other words, the symbol rows drawn on the reel band are scrolled in a downward direction in each of the reel display portion  101  through  105  (refer to  FIG. 10 ). 
     After a predetermined period has passed, the reel band in each reel display portion  101  through  105  is stopped and displayed. Consequently, one portion of the symbol row constituting each reel band (specifically, three symbols constituting each reel band) is stopped on each of the reel display portion  101  through  105 . In other words, as shown in  FIG. 11 , each one symbol is stopped in the three symbol display areas constituting each reel display portion. As a result, the variable display portion  3 D stops and displays fifteen symbols (refer to  FIG. 11 ). 
     As was described above, in the game according to the present embodiment, a winning combination is determined based on the number of identical symbols displayed on the variable display portion  3 D, and a prize corresponding to the winning combination is awarded. In the event of a winning combination, an amount obtained by multiplying the payout amount in accordance with the winning combination by the bet amount will be awarded to the player (refer to  FIG. 12 ). This will be further described in more detail. 
     Next, the contents of the winning combination and the prize in the slot machine  1  according to the present embodiment will be described while referring to the drawings.  FIG. 12  is an explanatory diagram showing a payout table according to the present embodiment. 
     As shown in  FIG. 12 , the payout table contains associations between the winning combination and prize to be awarded (specifically, the payout amount). The payout amount in the payout table shown in  FIG. 12  shows the payout amount in the case the amount of bets is “1”. Specifically, if the amount of bets is “2” or more, an amount obtained by multiplying the bet amount by the payout amount shown in  FIG. 12  will be paid out. 
     For instance, if five “TREASURE” symbols  45 C are displayed in the fifteen symbol display areas (e.g., symbol display areas  111 A through  111 C,  112 A through  112 C,  113 A through  113 C,  114 A through  114 C,  115 A through  115 C) in the variable display portion  3 D, “an amount obtained by multiplying the amount of bets by  200  credits” will be paid out to the player (refer to  FIG. 12 ). 
     If four “KING” symbols  45 K are displayed on the fifteen symbol display areas in the variable display portion  3 D, “an amount obtained by multiplying the bet amount by 40 credits” will be paid out to the player (refer to  FIG. 12 ). A payout amount is set for each winning combination in a similar manner, as shown in  FIG. 12 . 
     As shown in  FIG. 12 , the highest payout amount is set for the winning combination corresponding to the “WEREWOLF” symbol  50 , as compared to the other symbols. Accordingly, when the “HUMAN” symbol  45 B is changed into the “WEREWOLF” symbol  50 , the player is awarded the highest payout. 
     If three or more “MOON” symbols  45 A are displayed on the fifteen symbol display areas in the variable display portion  3 D, the slot machine  1  awards a bonus game to the player, instead of a payout amount. In the present embodiment, a so-called “free game” is awarded to the player as a bonus game. Here, the free game is a game that can be executed without the need for the player to bet new credits. 
     The case in which the symbols displayed on fifteen symbol display areas in the variable display portion  3 D do not correspond to any of the winning combinations shown in  FIG. 12  is regarded as a miss. In this case, no payout and award are made with respect to a miss. 
     The payout table shown in  FIG. 12  represents one example thereof. Accordingly, the type of the winning combination and the contents of the prize can be set as is appropriate. For instance, the payout amount can be set appropriately as the contents of the prize. And, a bonus game (for instance, a selective bonus game and the like) of a different type than the free game or a JACKPOT can be awarded as prize in the slot machine  1 . Further, a plurality of payout tables can be provided and selection is made possible in accordance with the payout rate. 
     Next, the main control program which is executed in the slot machine  1  according to the present embodiment will be described while referring to the accompanying drawings.  FIG. 13  is a flow chart of a main control program. 
     When the power switch is turned on (the power is turned on), the main control board  71  and the sub-control board  72  are activated respectively. And then, the controller  41  executes an initial setting process (S 1 ). In the initial setting process (S 1 ), the main CPU  42  executes the BIOS stored in the ROM  44  and expands the compressed data incorporated in the BIOS in the RAM  43 . In executing the BIOS that was expanded in the RAM  43 , the main CPU  42  carries out a diagnosis and initialization of the different types of peripheral devices. Further, the main CPU  42  writes the game programs and the like from the ROM  44  into the RAM  43 . The main CPU  42  acquires payout rate setting data and country identification information. While executing the initial setting process (S 1 ), the main CPU  42  also carries out an authentication process with respect to each program. 
     When the initial setting process (S 1 ) ends, the main CPU  42  executes a main game process (S 2 ). In this main game process (S 2 ), the main CPU  42  sequentially reads the game programs and the like from the RAM  43  and executes these programs. The slot machine  1  according to the present embodiment carries out the game by executing this main game process (S 2 ). 
     The main game process (S 2 ) is repeatedly executed while power is supplied to the slot machine  1 . 
     Next, the main game process program which is executed in the main game process (S 2 ) will now be described while referring to the drawings.  FIG. 14  is a flow chart of a main game process program to be executed in the slot machine  1  according to the present embodiment. The programs shown in the following flow chart are stored in the ROM  44  and RAM  43  provided in the slot machine  1  and are executed in the main CPU  42 . 
     As shown in  FIG. 14 , the main CPU  42  first executes a start acceptance process (S 11 ). In the start acceptance process (S 11 ), the player inserts coins and carries out a betting operation using the BET button from amongst the operation buttons  26 . 
     After shifting to step S 12 , the main CPU  42  determines whether the start button from amongst the operation buttons  26  has been depressed or not. The main CPU  42  determines the presence or absence of input with respect to the start button, in accordance with the presence or absence of a signal based on depressing the start button. If the start button has been depressed (S 12 : YES), the main CPU  42  stores the bet information in the RAM  43 . This bet information shows the amount of bets that was set based on the above bet operation. At this time, the main CPU  42  subtracts the above bet amount from the credit amount that the player currently possesses. After subtraction of the credit amount and storing of the bet information have ended, the main CPU  42  shifts the flow to step S 13 . On the other hand, if the start button has not been depressed (S 12 : NO), the main CPU  42  returns the flow to the start acceptance process (S 11 ). As a result, the player can carry out an operation to correct, etc. the bet amount. 
     After shifting to step S 13 , the main CPU  42  executes a symbol lottery process. In this symbol lottery process (S 13 ), the main CPU  42  executes the lottery program stored in the RAM  43 , thereby sampling a random number value from a number value range within a predetermined random number value range. The main CPU  42  determines the symbols that are stopped at the central portion in each reel display portion (specifically, symbol display areas  111 B,  112 B,  113 B,  114 B and  115 B) based on the sampled random number value and table. The main CPU  42  determines the symbols that were stopped at the upper portion and lower portion of the reel display portion based on determining the symbols stopped at the central part of the reel display portion. 
     Here, a process using the random number value in the symbol lottery process (S 13 ) will now be described based on the drawings.  FIG. 15  shows one example of a table including associations between the symbols drawn on any one reel band and the code numbers.  FIG. 16  shows one example of a table including associations between the random number values and the code numbers. 
     These tables containing associations between the symbols and the code numbers (for instance,  FIG. 15 ) exist in association with each of the reel display portions  101  through  105 . 
     As was described above, in the symbol lottery process (S 13 ), the main CPU  42  executes a lottery program, thereby sampling a random number value from a predetermined random number range (for instance, 0 through 65535). Thereafter, the main CPU  42  determines the code numbers based on the sampled random number value and a table including associations between the random number values and the code numbers (refer to  FIG. 16 , for instance). After the code numbers have been determined, the main CPU  42  determines the symbols to be stopped in the central part of the reel display portion based on the code numbers and the table including associations between the symbols and code numbers (refer to  FIG. 15 ). 
     For instance, when the reel band shown in  FIG. 15  is used with respect to the reel display portion  101 , if the random number value “1136” is sampled, the main CPU  42  decides for the code number “08” based on the random number vale “1136” and the table shown in  FIG. 16 . Then, the main CPU  42  decides the symbol which will be stopped on the symbol display area  111 B to be “10” symbol  45 H based on the code number “08” and the table shown in  FIG. 15 . 
     In this case, the “MEAT” symbol  45 D (code number:  7 ) is determined to be the symbol which will be stopped on the symbol display area  111 A that constitutes the upper portion of the reel display portion  101 . The “MOON” symbol  45 A (code number:  9 ) is determined to be the symbol that will be stopped on the symbol display area  111 C that constitutes the lower portion of the reel display portion  101 . 
     The process using the random number value in the symbol lottery process (S 13 ) is not limited to the instance of using the random number value, the table including associations between the random number values and the code numbers (refer to  FIG. 16 , for instance) and the table including associations between the symbols and the code numbers (refer to  FIG. 15 ). 
     For instance, the sampled random number value and the symbols may be directly associated. Alternatively, the sampled random number values and the winning combinations can be directly associated to thereby allow determination of the symbol to be stopped using the table. Here, the case that a random number value which is not associated with a winning combination is sampled is regarded as a miss. 
     The processes in executing the main game process program following the symbol lottery process (S 13 ) will next be described while referring again  FIG. 14 . 
     After the symbol lottery process (S 13 ) ends, the main CPU  42  determines (S 14 ) whether a special winning combination has been established based on the lottery results of the symbol lottery process (S 13 ). This special winning combination is a winning combination corresponding to the “HUMAN” symbol  45 B (refer to  FIG. 12 ). Accordingly, the main CPU  42  determines whether three or more “HUMAN” symbols  45 B are stopped on the variable display portion  3 D based on the lottery results in the symbol lottery process (S 13 ). If a special winning combination is established (S 14 : YES), the main CPU  42  shifts the flow to the symbol change lottery process (S 15 ). On the other hand, if a special winning combination is not established (S 14 : NO), the main CPU  42  shifts the flow to the game result display process (S 16 ). 
     After shifting to step S 15 , the main CPU  42  executes the symbol change lottery process. In the symbol change lottery process (S 15 ), the main CPU  42  executes the symbol change lottery process program that will be described later. Then, the main CPU  42  determines whether to change the “HUMAN” symbol  45 B stopped on the variable display portion  3 D to the “WEREWOLF” symbol  50  (i.e. to change a symbol or not) through a lottery. The main CPU  42  determines the timing of this symbol change through lottery. The symbol change lottery process (S 15 ) will be described in detail later. When the symbol change lottery process (S 15 ) ends, the main CPU  42  shifts the flow to step S 16 . 
     The game results in the slot machine  1  are determined in principle by the lottery results of the symbol lottery process (S 13 ). If a special winning combination is established, the game results in the slot machine  1  are determined based on the lottery results of the symbol lottery process (S 13 ) and the symbol change lottery process (S 15 ). 
     After shifting to step S 16 , the main CPU  42  executes a game result display process. In this game result display process (S 16 ), the main CPU  42  executes a game result display process program that will be described later. In the game result display process (S 16 ), the main CPU  42  variably displays the symbols on the variable display portion  3 D and stops each symbol corresponding to the game results on the variable display portion  3 D. The game result display process (S 16 ) will be described in detail later. After the game result display process (S 16 ) ends, the main CPU  42  shifts the flow to step S 17 . 
     In the game result display process (S 16 ), the main CPU  42  executes image effects in the background display portion  3 E and the change from the “HUMAN” symbol  45 B into the “WEREWOLF” symbol  50 , based on the lottery result of the symbol change lottery process (S 16 ). 
     After shifting to step S 17 , the main CPU  42  determines whether a winning combination has been established in the variable display portion  3 D. In a normal case, the main CPU  42  carries out the determination at step S 17  based on the lottery results of the symbol lottery process (S 13 ). When the symbol change lottery process (S 15 ) is executed, the main CPU  42  carries out the determination at step S 17  based on the lottery results of the symbol lottery process (S 13 ) and the lottery results of the symbol change lottery process (S 15 ). 
     In case a winning combination is established (S 17 : YES), the main CPU  42  calculates the payout amount corresponding to the winning combination based on the payout table (refer to  FIG. 12 ). Accordingly, if the “HUMAN” symbol  45 B is changed to the “WEREWOLF” symbol  50 , the main CPU  42  adds the payout amount corresponding to the “WEREWOLF” symbol  50  to the payout amount corresponding to another winning combination that was established. After the calculated payout amount is stored in the RAM  43 , the main CPU  42  shifts the flow to step S 18 . On the other hand, if no winning combination is established (S 17 : NO), the main CPU  42  shifts the flow to step S 19 . 
     After shifting to step S 18 , the main CPU  42  executes a payout process. In this payout process (S 18 ), the main CPU  42  pays out the payout amount calculated at step S 17  to the player. Accordingly, in the event a symbol change was carried out, the player is awarded the highest payout based on the winning combination with respect to the “WEREWOLF” symbol  50 . After the payout process (S 18 ) is ended, the main CPU  42  shifts the flow to step S 19 . 
     In step S 19  that follows, the main CPU  42  determines whether a bonus game trigger has been established. The bonus game trigger in the present embodiment refers to the case that “three or more “MOON” symbols 45A are stopped and displayed on the variable display portion 3D”. Accordingly, the main CPU  42  carries out the determination process at step S 19  based on the lottery results in the symbol lottery process (S 13 ). In the event a bonus game trigger has been established (S 19 : YES), the main CPU  42  shifts the flow to a bonus game process (S 20 ). On the other hand, in the event the bonus game trigger has not been established (S 19 : NO), the main CPU  42  ends the main game process program. As was described in the above text, the main game process program ends, and simultaneously with its ending, the program is re-executed. 
     After shifting to step S 20 , the main CPU  42  executes a bonus game process. In the bonus game process (S 20 ), the main CPU  42  executes a free game constituted of a predetermined number of unit games. Here, the unit game refers to a game executed in a sequence of processes from when variable display of each reel band starts until all the reel bands are stopped. After the free game has been executed, the main CPU  42  ends the bonus game process and then ends the main game process program. In this case as well, the main game process program ends, and simultaneously with its ending, the program is re-executed. 
     The processes relating to the free game are already in the public domain, and therefore, a detailed description of the bonus game process (S 20 ) is hereby omitted. 
     Next, the symbol change lottery process program which is executed in the symbol change lottery process (S 15 ) will be described in detail while referring to the drawings.  FIG. 17  is a flow chart of a symbol change lottery process program according to the present embodiment. 
     After shifting to the symbol change lottery process (S 15 ), the main CPU  42  executes the display content lottery process (S 31 ). In this display content lottery process (S 31 ), the main CPU  42  determines whether “the “HUMAN” symbol 45B which is stopped on the variable display portion 3D should be changed to the “WEREWOLF” symbol 50” by a lottery. More specifically, the main CPU  42  samples one random number value from a predetermined random number value range, by executing the lottery program. The main CPU  42  determines the presence or absence of a symbol change based on the sampled random number value and the display content lottery table (refer to  FIG. 18 ). After the lottery results of the display content lottery process (S 31 ) are stored in the RAM  43 , the main CPU  42  shifts the flow to step S 32 . 
     After shifting to step S 32 , the main CPU  42  determines whether the lottery result of the display content lottery process (S 31 ) is “with symbol change”. More specifically, the main CPU  42  carries out the process at step S 32  based on the lottery results of the display content lottery process (S 31 ) which is stored in the RAM. If the lottery result is “with symbol change” (S 32 : YES), the main CPU  42  shifts the flow to step S 33 . On the other hand, if the lottery result is “without symbol change” (S 32 ), the main CPU  42  ends the symbol change lottery process program as is. 
     At step S 33 , the main CPU  42  executes an effect timing determination process. In this effect timing determination process (S 33 ), the main CPU  42  determines the execution timing for the special effects which are carried out by the background display portion  3 E, through lottery. The special effects represent image effects to be carried out on the background display portion  3 E prior to the symbol change in case the symbol change is to be executed. 
     More specifically, the main CPU  42  first samples one random number value from the predetermined random number value range by executing the lottery program. The main CPU  42  determines the timing for execution of special effects based on the sampled random number value and the effect timing determination table (refer to  FIG. 19 ). After the effect timing thus determined is stored in RAM  43 , the main CPU  42  shifts the flow to step S 34 . 
     As shown in  FIG. 19 , the effect timing determination table defines two types of effect timing (specifically, a first effect timing and a second effect timing). The first effect timing shows a timing prior to variable display of the symbols in the variable display portion  3 D. The second effect timing shows a timing following display of the stopped symbols on the variable display portion  3 D, but prior to execution of symbol change. The first effect timing and the second effect timing are associated with random number value ranges that differ from one another. 
     After shifting to step S 34 , the main CPU  42  determines whether the first effect timing was determined in the effect timing determination process (S 33 ). If the first effect timing is determines (S 34 : YES), the main CPU  42  shifts the flow to step S 35 . On the other hand, if the second effect is determined (S 34 : NO), the main CPU  42  shifts the flow to step S 36 . 
     At step S 35 , the main CPU  42  executes a first effect flag storing process. In the first effect flag storing process (S 35 ), the main CPU  42  stores a first effect flag in the RAM  43  based on the process results of the effect timing determination process (S 33 ). This first effect flag shows that the timing for execution of the special effects is the first effect timing. After the first effect flag has been stored in the RAM  43 , the main CPU  42  ends the symbol change lottery process program. 
     On the other hand, at step S 36 , the main CPU  42  executes the second effect flag storing process. In the second effect flag storing process (S 36 ), the main CPU  42  stores the second effect flag in the RAM  43  based on the process results of the effect timing determination process (S 33 ). This second effect flag shows that the timing for executing the special effects is the second effect timing. After the second effect flag has been stored in the RAM  43 , the main CPU  42  ends the symbol change lottery process program. 
     Next, the game result display process program executed in the game result display process (S 16 ) will be described in detail while referring to the drawings.  FIG. 20  is a flow chart of a game result display process program. 
     After shifting to the game result display process (S 16 ), the main CPU  42  determines whether the first effect flag has been stored in the RAM  43  (S 41 ). If the first effect flag is stored in the RAM  43  (S 41 : YES), the main CPU  42  shifts the flow to step S 42 . On the other hand, if the second effect flag is stored in the RAM  43  (S 41 : NO), the main CPU  42  shifts the flow to step S 43 . 
     At step S 42 , the main CPU  42  carries out the special effect execution process. In this special effect execution process (S 42 ), the main CPU  42  executes the special effects by controlling the image control circuit  81  and the like. Once the execution of the special effects ends, the main CPU  42  shifts the flow to step S 43 . 
     The contents of the special effects executed in the special effects execution process will now be described in detail while referring to the drawings. In the slot machine  1 , normal effects and special effects are executed in accordance with the progress of the slot game. Normal effects include effects executed in a period until execution of the special effect execution process starts. In other words, in the event of no symbol change, the slot machine  1  carries out normal effects in accordance with the progress of the slot game (refer to  FIG. 10  and  FIG. 11 ). The special effects are carried out in accordance with the progress of the game based on the special effect execution process. The special effects are executed following the special effect execution process and until the unit game is ended. 
     First, the normal effects executed in the slot machine  1  according to the present embodiment will now be described. In the event of no symbol change, the normal effects are executed in the main display area  3 B and the like during execution of the unit game (refer to  FIG. 10  and  FIG. 11 ). In the event of a symbol change as well, the normal effects are executed in the main display area  3 B or the like until the special effect execution process is started (refer to  FIG. 1  and  FIG. 10 ). 
     When the normal effects are executed, a normal background image  90  is displayed on the background display portion  3 E. This normal background image  90  has a crescent moon image  91  and a cloud image  92 . At this time, the slot machine  1  executes the normal effects including image effects by use of the upper display portion  3 A and the like, illumination effects by use of the light emitting portion  25  and audio effects by use of the speaker  34 . 
     Next, the contents of the special effects which are executed in the slot machine  1  according to the present embodiment will now be described. As was described above, the slot machine  1  executes the normal effects until the special effect execution process starts. Accordingly, upon shifting to the special effect execution process, the background display portion  3 E displays the normal background image  90 . 
     Then, after the special effects execution process starts, the cloud image  92  in the normal background image  90  is displayed while being moved towards the crescent moon image  91 . Then, the cloud image  92  is displayed so as to hide the crescent moon image  91 . Once the crescent moon image is hidden behind the cloud image  92 , the display on the background display portion  3 E is changed from the normal background image  90  to the special background image  95  (refer to  FIG. 1 ). 
     As shown in  FIG. 1 ,  FIG. 21  and  FIG. 22 , the special background image  95  has a full moon image  96 . The special background image  95  does not contain the crescent moon image  91 . Accordingly, the player can grasp whether the special effects have been executed or not, based on the presence or absence of the crescent moon image  91  and the full moon image  96 . The slot machine  1  can enhance the sense of anticipation of the player with respect to symbol change by executing the special effects. 
     At this time, the slot machine  1  executes the special effects including image effects by use of the upper display portion  3 A and the like, illumination effects by use of the light emitting portion  25  and audio effects by use of the speaker  34 . Description of these effects is hereby omitted. The contents of the special effects can be changed in various manners. For instance, special effects can include displaying animation images that show the transformation process of a human into a werewolf onto the upper display portion  3 A. During the special effects, a sound effect such as the howling of a wolf can also be outputted. 
     After shifting to step S 43 , the main CPU  42  executes a spinning reel display process. In this spinning reel display process (S 43 ), the main CPU  42  variably displays each reel band at a predetermined speed on the reel display portions  101  through  105 . After the variable display of the reel band is started, the main CPU  42  shifts the flow to step S 44 . 
     At step S 44 , the main CPU  42  executes a stopped symbol display process. In this stopped symbol display process (S 44 ), the main CPU  42  stops each one symbol and displays the stopped symbol on each symbol display area that constitutes the variable display portion  3 D based on the lottery results of the symbol lottery process (S 13 ) (refer to  FIG. 11 ,  FIG. 21  and the like). After fifteen symbols are stopped on the variable display portion  3 D based on the lottery results in the symbol lottery process (S 13 ), the main CPU  42  shifts the flow to step S 45 . Even in the case where the symbol change is executed, the main CPU  42  stops symbols based only on the lottery result of the symbol lottery process (S 13 ). 
     In the present embodiment, after the passage of a predetermined time period from the start of the variable symbol display, the main CPU  42  stops the reel bands on the reel display portions  101  through  105  in a predetermined sequence. The reel bands may be stopped on all the reel display portions at the same time, or it may be stopped in sequence with a certain time lag. 
     At step S 45 , the main CPU  42  determines whether the second effect flag is stored in the RAM  43 . If the second effect flag is stored in the RAM  43  (S 45 : YES), the main CPU  42  shifts the flow to step S 46 . On the other hand, if the second effect flag is not stored in the RAM  43  (S 45 : NO), the main CPU  42  shifts the flow to step S 47 . 
     At step S 46 , the main CPU  42  carries out a special effect execution process. In this special effect execution process (S 46 ), the main CPU  42  executes special effects by controlling the image control circuit  81  and the like, in a manner similar with the above-described special effect execution process (S 42 ). The contents of the special effects have already been described, and therefore further description thereof is hereby omitted. After execution of the special effects is ended, the main CPU  42  shifts the flow to step S 47 . 
     After shifting to step S 47 , the main CPU  42  determines whether a symbol change is carried out in the current unit game. More specifically, the main CPU  42  carries out the process at step S 47  based on the lottery result of the display content lottery process (S 31 ) which is stored in the RAM  43 . If “the lottery result: with symbol change” (S 47 : YES), the main CPU  42  moves the flow to step S 48 . On the other hand, if “the lottery result: without symbol change” (S 47 : NO), the main CPU  42  ends the game result display process program as is. In this case, the variable display portion  3 D shows the symbols based only on the lottery result of the symbol lottery process (S 13 ). 
     At step S 48 , the main CPU  42  executes the symbol change process. In this symbol change process (S 48 ), the main CPU  42  changes the “HUMAN” symbol  45 B which is stopped on the variable display portion  3 D (refer to  FIG. 1  and  FIG. 21 ) into the “WEREWOLF” symbol  50  (refer to  FIG. 1  and  FIG. 22 ). After the “HUMAN” symbol  45 B has been changed into the “WEREWOLF” symbol  50 , the main CPU  42  ends the game result display process program. 
     As was described above, this symbol change process (S 48 ) is executed in the case that the lottery result of the display content lottery process (S 31 ) is “with symbol change”. The display content lottery process (S 31 ) is executed in the event a special winning combination is established (S 14 : YES). Accordingly, after shifting to this symbol change process (S 48 ), a plurality of “HUMAN” symbols  45 B are necessarily stopped on the variable display portion  3 D (refer to  FIG. 21 ). 
     The main CPU  42  can identify the respective types of the fifteen symbols which are stopped on the variable display portion  3 D based on the code numbers determined in the symbol lottery process (S 13 ) and the table including associations between the symbols and the code numbers (refer to  FIG. 15 ). That is, the main CPU  42  can identify the “HUMAN” symbol  45 B that was stopped on the variable display portion  3 D and the symbol display area onto which the “HUMAN” symbol  45 B was stopped. As a result, the main CPU  42  can change the “HUMAN” symbol  45 B that was stopped on the variable display portion  3 D into the “WEREWOLF” symbol  50  (refer to  FIG. 22 ). 
     The main CPU  42  executes a variety of effects simultaneously with the change of the “HUMAN” symbol  45 B into the “WEREWOLF” symbol  50 . For instance, animation images showing the transformation process of a human into a werewolf can be displayed on the upper display portion  3 A and the like in synchronization with the timing of the symbol change. 
     As was described above, the slot machine  1  according to the present embodiment determines the fifteen symbols that will be stopped on the variable display portion  3 D through the symbol lottery process (S 13 ). Then, the slot machine variably displays and stops symbols on the variable display portion  3 D. The slot machine  1  awards a prize based on the number of identical symbols which were stopped as a game result. 
     If the establishment of a special winning combination with respect to the “HUMAN” symbol  45 B is determined in the symbol lottery process (S 13 ), the slot machine  1  executes the display content lottery process (S 31 ). The slot machine  1  stops the symbols on the variable display portion  3 D based on the lottery result of the symbol lottery process (S 13 ). 
     At this time, if a determination of “with symbol change” is made in the display content lottery process (S 31 ), the slot machine  1  changes the “HUMAN” symbol  45 B which is stopped on the variable display portion  3 D into the “WERWWOLF” symbol  50  to which the high payout has been associated (S 48 ). Then, the slot machine  1  awards a prize to the player based on the symbol which is stopped on the variable display portion  3 D. Accordingly, the player can be granted a high payout based on the “WEREWOLF” symbol  50 . As a result, the slot machine  1  can provide new game characteristics in response to the demands of the players that desire a high payout. 
     The slot machine  1  carries out special effects prior to the symbol change (S 48 ) in the event of a win in the display content lottery process (S 31 ) (S 32 : YES). In the special effects, the normal background image  90  in the background display portion  3 E is changed to the special background image  95 . As a result, the player can understand that the probability of a symbol change is high before the symbol change occurs. Accordingly, the slot machine  1  can enhance the sense of anticipation of the player with respect to the symbol change (i.e. award of a high payout). 
     In this case, the slot machine  1  determines the timing for execution of the special effects through the effect timing determination process (S 33 ). The slot machine then executes the special effects (S 42  and S 46 ) at a timing (first effect timing or second effect timing) determined in the effect timing determination process (S 33 ). Accordingly, the slot machine  1  can diversify the timing for execution of the special effects. As a result, the slot machine  1  can further enhance the sense of anticipation with respect to the presence or absence of special effects (i.e. sense of anticipation with respect to being awarded a high payout). 
     The present invention is not limited to the above-described embodiment and various modifications and alterations can be made thereto without departing from the scope of the present invention. 
     For instance, the present invention is not limited to the aspect of determining the contents of the prize based on the number of identical symbols which were stopped on the variable display portion  3 D. That is, it is possible to employ the aspect in which the contents of the prize are determined based on the combination of the symbols that were stopped on the pay line defined in the variable display portion  3 D. 
     In the present embodiment, the “HUMAN” symbol  45 B changes into the “WEREWOLF” symbol  50  which is not included in the symbols constituting the reels (refer to  FIG. 7 ). However, this is not limited to this instance. That is to say, the “HUMAN” symbol  45 B can also be change into the symbol constituting the reels. In this case as well, this change is preferably made so as to allow a high payout award. 
     The effect timing determination process is not limited to the aspect in which the special effect timing is determined to be any of the first effect timing and the second effect timing. That is, the timing of the special effects may be determined from a plurality of effect timings. Also, the “case in which special effects are not executed” may be included in the effect timings determined in the effect timing determination process. 
     The symbol change (S 48 ) and the special effects (S 42 , S 46 ) may be executed in the free game according to the bonus game process (S 20 ). 
     Further, the present invention can also be realized as a game method for executing the above-described processes. Furthermore, the invention can also be realized as a program that causes execution of the game method on a computer, and a recording medium onto which this program has been recorded. 
     Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.