Patent Publication Number: US-2009227340-A1

Title: Slot Machine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority of U.S. Provisional Application No. 61/034,616 filed on Mar. 7, 2008. The contents of this application are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a slot machine. 
     2. Description of the Related Art 
     Conventionally, slot machines known as a type of gaming machines are constituted so as to: start games by players inserting coins or the like into the gaming machine; variably display columns of symbols in predetermined regions of the gaming machine while they are displayed in a stopped state after a predetermined period has elapsed; and award payout based on a combination of symbols in a stopped state. 
     In addition, the above slot machines are generally constituted to judge whether or not a winning combination allowed to award payout is established, based on whether or not a predetermined number of symbols of the same type (for example, “CHERRY” or “7”) are arranged along a preset payline. In the conventional slot machine, in a case where a predetermined number or more of symbols of the same type are arranged, it has been a common routine to award payout based on the number of the aforementioned arranged symbols, regardless of the payout line. 
     Further, many of the conventional slot machines have been known which conduct two types of games, i.e., a basic game and a free game. The basic game is executed upon consumption of gaming values (such as coins or credits) corresponding to the amount of bet. On the other hand, the free game is executed without consuming gaming values corresponding to the amount of bet. 
     The basic game is switched to the free game when a predetermined condition is met. The condition includes a case in which, for example, a specific symbol is displayed in a stopped state during the basic game. The free game is switched to the basic game when a predetermined condition is met. The condition includes a case in which, for example, the free games are executed a predetermined number of times. 
     In the conventional slot machines, it has been a common routine to raise players&#39; feeling of expectation for the free game by changing arrangement of symbols during the free game differently from that during the basic game. For example, U.S. Pat. No. 6,394,902-B1 describes a slot machine in which a total of fifteen symbols are displayed in three rows and five columns with the use of video reels. This slot machine changes symbol columns arranged on reels during the free game differently from that during the basic game, in which eight types of symbols are decreased to five. In this manner, a probability of awarding payout can be apparently increased during the free game. 
     In the aforementioned conventional slot machines, however, irrespective of whichever of the basic game and the free game is in progress, the symbols of different types have been randomly arranged in combination and sequential order. These slot machines determine the contents of the prize to be awarded, based on a combination of multiple symbols that have been arranged in a display device. Therefore, players are allowed to have the feeling of expectation only for random payout based on a combination of plural types of symbols that have been randomly arranged in the display device. Accordingly, a need exists for the advent of a slot machine which can offer new entertainability. 
     The present invention has been made in view of the above-described circumstance. It is an object of the present invention to provide a novel slot machine by enhancing entertainability associated with arrangement of the symbols during the free game. 
     SUMMARY OF THE INVENTION 
     A first aspect of the present invention is a slot machine including: a display device displaying a symbol matrix display region in which plural types of symbols are displayed; a control panel for receiving operation by a player; a memory for storing data concerning a number of predetermined symbols arranged in the symbol matrix display region; and a processor for controlling the display device and the memory, the processor being programmed to: (a) detect operation of the control panel; (b) execute a basic game; (c) determine an appearance frequency with which the predetermined symbol out of the plural types of symbols is rearranged in the symbol matrix display region in accordance with an operation status of the control panel during the basic game; (d) rearrange the plural types of symbols in the symbol matrix display region so as to rearrange the predetermined symbol within a range of the determined appearance frequency during the basic game; (e) cumulatively store data concerning a number of the predetermined symbols rearranged in the symbol matrix display region in the memory during the basic game; (f) determine a number of times in executing a free game by referring to the memory, in accordance with the data concerning the number of the predetermined symbols rearranged in the symbol matrix display region during the basic game; and (g) execute the free game by the determined number of times in a case where a predetermined condition is met during the basic game. 
     According to the first aspect of the present invention, when a predetermined control panel such as a MAX-BET button or a side-BET button is operated during the basic game, a frequency is determined, with which the predetermined symbol is rearranged. Within a range of the determined frequency, the predetermined symbol is rearranged; the number of predetermined symbols having been rearranged is cumulatively stored; and the free game is executed by the number of times in accordance with the stored number. Thus, players visually confirm the number of predetermined symbols rearranged during the basic game, thereby being able to raise expectations for payout of a subsequent free game. In this manner, the slot machine is allowed to raise player&#39;s expectation for payout of the free game even during the basic game, thereby enhancing entertainability. 
     A second aspect of the present invention is a slot machine constituted as set fourth below. In the first aspect, the control panel is a bet button; and the processor, in the itemized (c), determines the appearance frequency of the predetermined symbol to be higher with an increased amount of bet. 
     According to the second aspect of the present invention, the appearance frequency of the predetermined symbol is determined to be higher as the bet amount increases. Therefore, the appearance frequency of the predetermined symbol is different between cases where ten coins are bet and where the fifteen coins are bet, for example. The appearance frequency of the predetermined symbol increases as players bet a larger amount, which makes it possible to obtain a large payout during the free game. In this manner, the slot machine enables players to play the basic game with expectations for payout of the free game, thereby enhancing entertainability. 
     A third aspect of the present invention is a slot machine constituted as set forth below. In the second aspect, the processor, in the itemized (g), executes the free game by a total number of times which is obtained by summing a preset number of times to the number of times in executing the free game that is determined in the itemized (f). 
     According to the third aspect of the present invention, the determined number of times in executing the free game is added to the cumulatively stored number of times when the predetermined symbol is rearranged, and the free game is executed by the summed total of these numbers of times. For example, in a case where the cumulatively stored number of times when the predetermined symbol is rearranged is four while the preset number of times in executing the free game is six, the free game is executed ten times. Therefore, the preset number of times in executing the free game is added to the number of times in executing the free game, which is certainly performed, the number being equal to the number of times when the predetermined symbol is rearranged, so that the slot machine is allowed to raise player&#39;s expectations for payout of the subsequent free game, thereby enhancing entertainability during the basic game. 
     A fourth aspect of the present invention is a slot machine including: a display device displaying a symbol matrix display region in which plural types of symbols are displayed; a bet button for receiving bet operation by a player; a memory for storing data concerning a number of predetermined symbols arranged in the symbol matrix display region; and a processor for controlling the display device and the memory, the processor being programmed to: (a) detect operation of the bet button; (b) execute a basic game; (c) determine the appearance frequency to be higher with an increased amount of bet, the appearance frequency with which the predetermined symbol out of the plural types of symbols is rearranged in the symbol matrix display region during the basic game; (d) rearrange the plural types of symbols in the symbol matrix display region so as to rearrange the predetermined symbol within a range of the determined appearance frequency during the basic game; (e) cumulatively store data concerning a number of the predetermined symbols rearranged in the symbol matrix display region in the memory during the basic game; (f) determine a number of times in executing a free game by referring to the memory, in accordance with the data concerning the number of the predetermined symbols rearranged in the symbol matrix display region during the basic game; and (g) execute the free game by the determined number of times in a case where a predetermined condition is met during the basic game. 
     According to the fourth aspect of the present invention, the appearance frequency with which the predetermined symbol is arranged is determined to be higher with an increased amount of bet during the basic game. The number of times in executing the free game is determined in accordance with the number of predetermined symbols that are rearranged during the basic games executed between the previous free game and the next free game. Thus, the slot machine allows player to play each basic game with expectations for high payout of the free game, thereby enhancing entertainability. 
     A fifth aspect of the present invention is a slot machine constituted as set forth below. In the fourth aspect, the processor, in the itemized (g), executes the free game by a total number of times which is obtained by summing a preset number of times to the number of times in executing the free game that is determined in the itemized (f). 
     According to the fifth aspect of the present invention, the number of predetermined symbols is cumulatively stored, the predetermined symbols being rearranged during the basic game with the appearance frequency which changes depending on the amount of bet. The determined number of times in executing the free game is added to the above cumulatively stored number, and the free game is executed by the summed total of these numbers of times. For example, in a case where the cumulatively stored number of times when the predetermined symbol is rearranged is four while the preset number of times in executing the free game is six, the free game is executed ten times. Therefore, the preset number of times in executing the free game is added to the number of times in executing the free game, which is certainly performed, the number being equal to the number of times when the predetermined symbol is rearranged, so that the slot machine is allowed to raise player&#39;s expectations for payout of the next free game, thereby enhancing entertainability during the basic game. 
     A sixth aspect of the present invention is a slot machine including: a display device displaying a symbol matrix display region in which plural types of symbols are displayed; a bet button for receiving bet operation by a player; a memory for storing data concerning a number of predetermined symbols arranged in the symbol matrix display region; and a processor for controlling the display device and the memory, the processor being programmed to: (a) detect operation of the bet button; (b) execute a basic game; (c) determine the appearance frequency to be higher with an increase amount of bet, the appearance frequency with which the predetermined symbol out of the plural types of symbols is rearranged in the symbol matrix display region during the basic game; (d) rearrange the plural types of symbols in the symbol matrix display region so as to rearrange the predetermined symbol within a range of the determined appearance frequency during the basic game; (e) cumulatively store data concerning a number of the predetermined symbols rearranged in the symbol matrix display region in the memory during the basic game; (f) determine a number of times in executing a free game in accordance with the data concerning the number of the predetermined symbols rearranged in the symbol matrix display region during the basic game by referring to the memory; and (g) execute the free game by a total number of times which is obtained by summing a preset number of times to the determined number of times in executing the free game in a case where a predetermined condition is met during the basic game. 
     According to the sixth aspect of the present invention, the appearance frequency with which the predetermined symbol is rearranged is determined to be higher with an increased amount of bet during each basic game. The number of predetermined symbols that are rearranged during the basic games executed between the previous free game and the next free game is cumulatively stored. The cumulatively stored number of predetermined symbols is added to the number of times in executing the free game, which is determined based on the data concerning the number of other predetermined symbols. The free game is executed by the summed total number of these numbers of times. Therefore, the preset number of times in executing the free game is added to the number of times in executing the free game, which is certainly performed, the number being equal to the number of times when the predetermined symbol is rearranged, so that the slot machine is allowed to raise player&#39;s expectations for payout of the next free game, thereby enhancing entertainability during the basic game. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view showing an exemplary symbol matrix during a basic game according to a first embodiment; 
         FIG. 2  is a perspective view schematically showing a frame format of a slot machine according to the first embodiment; 
         FIG. 3  is a block diagram depicting an internal construction of the slot machine shown in  FIG. 2 . 
         FIG. 4A  is a view showing an exemplary image displayed during the basic game in the slot machine shown in  FIG. 2 ; 
         FIG. 4B  is a view showing an exemplary image displayed during the basic game in the slot machine shown in  FIG. 2 ; 
         FIG. 5A  is a view showing an exemplary image displayed during the basic game in the slot machine shown in  FIG. 2 ; 
         FIG. 5B  is a view showing an exemplary image displayed during the basic game in the slot machine shown in  FIG. 2 ; 
         FIG. 6A  is a view showing an exemplary image displayed during the basic game in the slot machine shown in  FIG. 2 ; 
         FIG. 6B  is a view showing an exemplary image displayed during the basic game in the slot machine shown in  FIG. 2 ; 
         FIG. 7  is a flowchart showing a subroutine of a main process; 
         FIG. 8  is a flowchart showing a subroutine of a game execution process according to the first embodiment; 
         FIG. 9  is a flowchart showing a subroutine of a basic game symbol rearrangement process according to the first embodiment; 
         FIG. 10  is a flowchart showing a subroutine of a free game execution process according to the first embodiment; 
         FIG. 11  is a flowchart showing a subroutine of a free game termination process according to a second embodiment; 
         FIG. 12  is a view schematically showing a frame format of an appearance of a slot machine according to a third embodiment; 
         FIG. 13A  is a view showing an exemplary symbol matrix during a basic game according to the third embodiment; 
         FIG. 13B  is a view showing an exemplary symbol matrix during a basic game according to the third embodiment; and 
         FIG. 14  is a flowchart showing a subroutine of a basic game symbol rearrangement process according to the third embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First, a slot machine  10  according to a first embodiment will be described with referring to the drawings. The slot machine according to the first embodiment is a so-called video slot machine, which has an image display panel such as a liquid crystal display and executes a game by displaying images of various symbols on the image display panel. 
       FIG. 1  is a view showing an exemplary symbol matrix during a basic game according to the first embodiment. The slot machine  10  according to the present invention executes either one of two modes of games, i.e., a basic game and a free game. The basic game is executed upon consuming a gaming value corresponding to the amount bet by a player. The free game is executed without consuming a gaming value in a case where a predetermined condition is met during the basic game. During the basic game, the slot machine  10  is allowed to: detect operation of a control panel including a MAX-BET button  27  or the like; determine based on the operation of the control panel, a frequency with which a symbol “CHANCE  70   a ” serving as a predetermined symbol is rearranged in a symbol matrix element SM; rearrange the symbol “CHANCE  70   a ” within a range of the determined frequency; store in a memory data concerning the number of rearranged symbols “CHANCE  70   a ”; display an icon “CHANCE  70   c ” on a lower image display panel  16  based on the data concerning the number of rearranged symbols “CHANCE  70   a ” stored above; and determine the number of times in executing the free game. While the slot machine  10  is of a stand-alone type, which is not connected to a network, the present invention is also applicable to a networked slot machine. 
     As shown in  FIG. 1 , elements of the symbol matrix SM are displayed on the lower image display panel  16  described later, included in the slot machine  10 . The elements of the symbol matrix SM are made up of a total of fifteen symbols in three rows and five columns. 
     In the first embodiments of the present invention, any of symbols “main character  121 ”, “sub character  122 ”, “office building  123 ”, “gold bullion  124 ”, “car  125 ”, “stock certificate  126 ”, “jet  127 ”, “villa  128 ”, and “CHANCE  70   a ” are rearranged in the elements of symbol matrix SM. A payout is determined based on the number of symbols of respective types rearranged in the elements of the symbol matrix SM. 
     As shown in  FIG. 1 , during the basic game, when the symbol “CHANCE  70   a ” is rearranged upon rearranging the symbols, “main character  121 ”, “sub character  122 ”, “office building  123 ”, “gold bullion  124 ”, “car  125 ”, “stock certificate  126 ”, “jet  127 ”, “villa  128 ”, and “CHANCE  70   a ” in any of the elements of the symbol matrix SM, icons “CHANCE  70   b ” and “CHANCE  70   c ” are cumulatively displayed in a region on the lower image display panel  16  other than a region in which the elements of the symbol matrix SM are displayed. These icons are displayed so as to visualize the number of symbols “CHANCE  70   a ” which are rearranged until a next free game is started. In this case, the icon “CHANCE  70   b ” corresponding to the symbol “CHANCE  70   a ” that is rearranged during the current basic game is displayed in a blinking state at an upper portion of the elements of the symbol matrix SM so as to visualize rearrangement of the symbol “CHANCE  70   a ”. The icon “CHANCE  70   c ” indicates the presence of the symbol “CHANCE  70   a ” that has been rearranged during the previous basic game. 
       FIG. 2  is a view schematically depicting a frame format of an appearance of the slot machine according to the first embodiment. The gaming media used in the slot machine  10  include coins, bills, or electronic value information equivalent thereto. In the present invention, however, the gaming media are not limitative thereto in particular, and can include medals, tokens, electric money, and tickets, for example. The above tickets are not limitative in particular, and can include barcode-attached tickets or the like, as described later, for example. 
     The slot machine  10  is provided with a cabinet  11 , a top box  12  installed on an upper side of the cabinet  11 , and a main door  13  provided on a front surface of the cabinet  11 . 
     The lower image display panel  16  serving as a display device is provided in front of the main door  13 . The lower image display panel  16  is provided with a liquid crystal panel, which displays the fifteen elements of the symbol matrix SM in three rows and five columns. A single symbol is arranged in each of the elements of the symbol matrix SM. 
     A credit amount display section  31  of the lower image display panel  16  displays the number of coins credited by way of an image. A payout amount display unit  32  displays by way of an image the number of, for example, coins to be paid if a predetermined number or more symbols of respective types are rearranged in the elements of the symbol matrix SM. 
     Provided on a lower side of the lower image display panel  16  are a control panel  20  having a plurality of buttons  23  to  27  through which command regarding the process of the game will be input by a player, a coin receiving slot  21  for receiving coins into the cabinet  11 , and a bill validator  22 . 
     On the control panel  20 , a start button  23 , a change button  24 , a cashout button  25 , a 1-BET button  26 , a MAX-BET button  27 , and a side-BET button  85  are provided. The start button  23  is intended for entering a command for starting the game. The change button  24  is intended for use in asking an attendant of the gaming facility for change. The cashout button  25  is intended for entering a command for paying out the credited coins to a coin tray  18  through a coin payout exit  19 . 
     The 1-BET button  26  is intended for entering a command for betting one coin among the credited coins on the game. The MAX-BET button  27  is intended for entering a command for betting the upper number (50 in this embodiment) of coins that can be bet per game among the credited coins on the game. The side-BET button  85  is intended for entering a command for betting coins on the game if players desire to place a bet on one more game. 
     The bill validator  22  validates whether or not a bill is legitimate and accepts a legitimate bill into the cabinet  11 . The bill validator  22  may be configured so that a barcode-attached ticket  39  described later is readable thereby. Provided on a lower front surface of the main door  13 , that is, at a lower part of the control panel  20 , is a berry glass  34  on which characters of the slot machine  10  and the like are depicted. 
     On a front surface of the top box  12 , an upper image display panel  33  is provided. The upper image display panel  33  has a liquid crystal panel, which displays images for introducing the game contents or explaining game rules, for example. 
     Also, on the top box  12 , a speaker  29  and a lamp  30  are provided. On a lower side of the upper image display panel  33 , a ticket printer  35 , a card reader  36 , a data display unit  37 , and a key pad  38  are provided. The ticket printer  35  prints on the ticket, a barcode having encoded thereon data such as the credit amount, the date and time, and the identification number of the slot machine  10 , and outputs the printed ticket as the barcode-attached ticket  39 . The player can play the game on another slot machine with the barcode attached ticket  39  by causing this slot machine to read the barcode attached ticket  39 . Alternatively, the player can exchange the barcode-attached ticket  39  with the bills or the like at a predetermined place (at a cashier inside a casino, for example) of the gaming facility. 
     The card reader  36  reads data from and write data into a smart card. The smart card is to be owned by the player, which stores data for identifying the player or data regarding the log of games executed by the player, for example. The smart chard may store data corresponding to coins, bills, or a credit. As an alternative of a smart card, a magnetic stripe card may be employed. The data display  37  is made up of a fluorescent display and the like, and displays the data read by the card reader  36  or the data input by the player through the key pad  38 , for example. The key pad  38  inputs data and commands regarding the ticket issuance or the like. 
       FIG. 3  is a block diagram depicting the internal construction of the slot machine shown in  FIG. 2 . A gaming board  50  includes: a CPU (Central Processing Unit)  51 , a ROM (Read Only Memory)  55  and a boot ROM  52  interconnected by an internal bus; a card slot  53 S corresponding to a memory card  53 ; and an IC socket  54 S corresponding to a GAL (Generic Array Logic)  54 . 
     The memory card  53  is formed of a nonvolatile memory such as Compact Flash (registered trademark) and stores game programs. The game programs include a symbol selection program. The aforementioned symbol selection program is intended for determining the symbols to be rearranged in the elements of the symbol matrix SM. The aforementioned symbol selection program includes symbol weighing data respectively corresponding to plural types of payout ratios (80%, 84%, and 88%, for example). The symbol weighting data is indicative of the correspondence relationship between the respective symbols and one or more random numeric values which come under a predetermined numerical range (0 to 255). The payout ratio is determined according to the payout-ratio setting data output from the GAL  54 . The symbols to be rearranged in the elements of the symbol matrix SM are determined depending upon the symbol weighing data corresponding to this payout ratio. Further, the game programs include table data indicating the correspondence relationship between each of the symbols and a payout. 
     Also, the card slot  53 S is configured to allow the memory card  53  to be inserted thereinto or ejected therefrom, and is connected to a motherboard  40  through IDE pass. Accordingly, the memory card  53  can be ejected from the card slot  53 S, other game programs and other game system programs can then be written into the memory card  53 , and further, the memory card  53  can be inserted into the card slot  53 S, thereby allowing the player to change the types and contents of games executed in the slot machine  10 . The game program includes data concerning a game progress. Furthermore, the game program includes image data or sound data to be output during the game. The image data include, for example, image data indicative of the symbol matrix. 
     The GAL  54  is a type of a PLD having a fixed OR array structure. The GAL  54  includes plural input ports and plural output ports. Where predetermined data is input to the input port, the GAL  54  outputs data corresponding to the aforementioned data from the output port. The data output from this output port is equivalent to the aforementioned payout-ratio setting data. Further, the IC socket  54 S is configured to allow the GAL  54  to be attached thereto and detached therefrom, and is connected to the motherboard  40  by a PCI bus. Accordingly, the GAL can be replaced with the replacement GAL  54  to change the payout-ratio setting data. 
     The CPU  51 , the ROM  55 , and the boot ROM  52  interconnected by the internal bus are connected to the motherboard  40  by the PCI bus. The PCI bus serves to transmit signals between the motherboard  40  and the gaming board  50  and supply power from the motherboard  40  to the gaming board  50 . 
     The motherboard  40  is constructed using a general-purpose motherboard commercially available (a printed circuit board on which essential parts of a personal computer are mounted) and includes: a main CPU (Central Processing Unit)  41 , a ROM (Read Only Memory)  42 ; a RAM (Random Access Memory)  43 ; and a communication interface  44 . The main CPU  41  functions as a processor for controlling a display device and memory according to the embodiment of the present invention. 
     The ROM  42  is made up of a memory device such as a flash memory and stores thereon a program such as BIOS (Basic Input/Output System) executed by the main CPU  41 , and permanent data. When the BIOS is executed by the main CPU  41 , processing of initializing predetermined peripheral devices is carried out and processing of capturing game programs and game system programs stored in the memory card  53  through the gaming board  50  is started. In the present invention, the contents of the ROM  42  may be rewritable or not. 
     The RAM  43  stores data and a program used when the main CPU  41  is activated. The RAM  43  can also store game programs. The RAM  43  further stores data concerning the credit amount, the number of coin-in or coin-out for one game, and the like. 
     Both a main body PCB (Printed Circuit Board)  60  and a door PCB  80 , which will be described later, are connected to the motherboard  40  by USB. A power supply unit  45  is also connected to the motherboard  40 . 
     Connected to the main body PCB  60  and the door PCB  80  are: equipment and devices which generate input signals to be input to the main CPU  41 ; and equipment and devices of which operations are controlled by a control signal output from the main CPU  41 . The main CPU  41  executes a game program stored in the RAM  43  based on an input signal having been input to the main CPU  41  and performs a predetermined computational process, thereby storing results thereof in the RAM  43  or transmitting a control signal to each of equipment and devices as a control process therefor. 
     A lamp  30 , a hopper  66 , a coin detecting section  67 , a graphic board  68 , a speaker  29 , a touch panel  69 , the bill validator  22 , the ticket printer  35 , the card reader  36 , a key switch  38 S, and the data display unit  37  are connected to the main body PCB  60 . The lamp  30  is lit up in a predetermined pattern based on a control signal output from the main CPU  41 . 
     The hopper  66  is installed in the cabinet  11  and pays out a predetermined number of coins from the coin payout exit  19  to the coin tray  18  based on a control signal output from the main CPU  41 . The coin detecting section  67  is installed inside the coin payout exit  19  and outputs an input signal to the main CPU  41  upon detecting that a predetermined number of coins have been paid out from the coin payout exit  19 . 
     The graphic board  68  controls, based on a control signal output from the main CPU  41 , images to be displayed on the upper image display panel  33  and the lower image display panel  16 . The credit amount stored in the RAM  43  is displayed on a credit amount display section  31  (see  FIG. 2 ) of the lower image display panel  16 . The number of coins to be paid out is displayed at a payout amount display section  31  (see  FIG. 2 ) of the lower image display panel  16 . The graphic board  68  is equipped with a VDP (Video Display Processor) which generates image data based on a control signal output from the main CPU  41  and a video RAM which temporarily stores image data generated by the VDP, and the like. The image data used in generating image data with VDP is contained in the game program read from the memory card  53  and stored in the RAM  43 . 
     The bill validator  22  validates whether or not a bill is legitimate and accepts a legitimate bill into the cabinet  11 . Upon accepting a legitimate bill, the bill validator  22  outputs an input signal to the main CPU  41  based on the amount of the bill. The main CPU  41  stores in the RAM  43  the credit amount corresponding to the amount of bills transmitted by the input signal. 
     Based on a control signal output from the main CPU  41 , the ticket printer  35  prints on a ticket a barcode having encoded thereon data such as the credit amount, data and time, and the identification number of the slot machine  10  stored in the RAM  43 . Further, this printer outputs the printed ticket as a barcode-attached ticket  39 . The card reader  36  transmits to the main CPU  41  the data read from the smart card and writes the read data onto the smart card, based on a control signal from the main CPU  41 . The key switch  38 S is provided on the key pad  38 , and outputs a predetermined input signal to the main CPU  41  when the player operates the key pad  38 . The data display  37 , based on a control signal output from the main CPU  41 , displays the data read by the card reader  36  and the data input by the player through the key pad  38 . 
     The control panel  20 , a reverter  21 S, a coin counter  21 C, and a cold cathode tube  81  are connected to the door PCB  80 . The control panel  20  is provided with: a start switch  23 S corresponding to the start button  23 ; a change switch  24 S corresponding to the change button  24 ; a cashout switch  25 S corresponding to a cashout button  25 ; a 1-BET switch  26 S corresponding to a 1-BET button  26 ; a MAX-BET switch  27 S corresponding to the MAX-BET button  27 ; and a side-BET switch  85 S corresponding to the side-BET switch  85 . When the player operates the buttons  23  to  27  and  85 , the corresponding switches  23 S to  27 S and  85 S output input-signals to the main CPU  41 , respectively. 
     The coin counter  21 C is provided inside the coin receiving slot  21 , and validates whether or not a legitimate coin is inserted into the coin receiving slot  21 . Those other than the legitimate coins are discharged from the coin payout exit  19 . The coin counter  21 C outputs an input signal to the main CPU  41  when a legitimate coin is detected. 
     The reverter  21 S operates based on a control signal output from the main CPU  41  and distributes coins recognized as being legitimate by the coin counter  21 C into a cash box (not shown in the drawings) or the hopper  66  which is arranged in the slot machine  10 . In other words, when the hopper  66  is filled with coins, legitimate coins are distributed by the reverter  21 S into the cash box. On the other hand, when the hopper  66  is not filled with coins, legitimate coins are distributed into the hopper  66 . The cold cathode tube  81  functions as a backlight installed on rear face side of each of the lower image display panel  16  and the upper image display panel  33 , and is lit up based on a control signal output from the main CPU  41 . 
       FIGS. 4A to 6B  are views each showing an exemplary image displayed in the slot machine shown in  FIG. 2  according to a second embodiment.  FIGS. 4A and 4B  are views each showing an exemplary image displayed during a basic game in the slot machine shown in  FIG. 2 . 
     As shown in  FIG. 4A , the lower image display panel  16  is made up of a display region  92 , an information display section  93 , an effect image display section  94 , and the like. The elements of the symbol matrix SM are displayed in the display region  92 . The information display section  93  is arranged upwardly of the display region  92  and is made up of a credit amount display section  93   a,  a BET amount display section  93   b,  a character information display section  93   c,  a PAID amount display section  93   d,  and a charge display section  93   e.    
     The number of coins currently credited is displayed at the credit amount display section  93   a  while the number of coins bet on one game is displayed at the BET amount display section  93   b.  The character information indicative of a current status of the game is displayed at the character information display section  93   c.  The characters of “PLAYNOW” are displayed during the play of the game, whereas the characters of “GAMEOVER” are displayed during the intervals between the plays of the game. The number of coins that have been successfully obtained in one game is displayed at the PAID amount display section  93   d,  whereas a conversion value of the credit amount based on a predetermined charge is displayed at the charge display section  93   e.    
     The effect image display section  94  displays effect images according to a type of the present slot game. In other words, the effect image display section  94  displays different effect images between the basic and free games. 
     Any of symbols, “main character  121 ”, “sub character  122 ”, “office building  123 ”, “gold bullion  124 ”, “car  125 ”, “stock certificate  126 ”, “jet  127 ”, “villa  128 ”, and “CHANCE  70   a ” are rearranged in the elements of the symbol matrix SM on the lower image display panel  16 . A payout is determined based on the number of these symbols rearranged in the elements of the symbol matrix SM. It should be noted that the symbol “CHANCE  70   a ” in this embodiment corresponds to “a predetermined symbol” set forth in Claims. 
     During the basic game, the symbols, “main character  121 ”, “sub character  122 ”, “office building  123 ”, “gold bullion  124 ”, “car  125 ”, “stock certificate  126 ”, “jet  127 ”, “villa  128 ”, and “CHANCE  70   a ” are rearranged in any of the elements of the symbol matrix SM. When the symbol “CHANCE  70   a ” is rearranged in this manner, the icon “CHANCE  70   b ” is displayed in a blinking state at the effect image display section  94  on the lower image display panel  16 . This icon is displayed so as to visualize the number of symbols “CHANCE  70   a ” which have been rearranged until the next free game is started. As shown in  FIG. 4B , after a predetermined period has elapsed, the icon is switched from “CHANCE  70   b ” to “CHANCE  70   c ” which is defined as an ordinary display. The display of icon may be set in a blinking state during an effect display or may be switched in an ordinary state when the effect display is completed. 
       FIGS. 5A and 5B  are views each showing an exemplary image displayed during the basic game in the slot machine shown in  FIG. 2 , relating to determination of start of the free game. As shown in  FIG. 5A , the display region  92  displays the elements of the symbol matrix SM. The free game is not started unless three or more symbols “main character  121 ” are displayed in the elements of the symbol matrix SM during the basic game. 
     As shown in  FIG. 5B , when three or more symbols “main characters  121 ” are displayed in the elements of the symbol matrix SM, the start of the free game is determined. At this time, the number of times in executing the free game from now on is also determined. The effect image display section  94  displays the icon “CHANCE  70   c ” indicative of the number of symbols “CHANCE  70   a ” that have been rearranged during a period from completion of the previous free game to start of the next free game to be executed from now on. 
       FIGS. 6A and 6B  are views each showing an exemplary image displayed during the free game in the slot machine  10  shown in  FIG. 2 . As shown in  FIG. 6A , when the free game is determined to be started, the upper image display panel  33  displays a free-game-number display image  90   b  indicative of the remaining number of times in executing the free game. In this case, the free-game-number display image  90   b  of “15FREE GAMES” is displayed indicating that fifteen free games remain. 
     As shown in  FIG. 6B , the display region  92  displays the elements of the symbol matrix SM, in which the symbols are rearranged in the respective elements of the symbol matrix SM by the number of times corresponding to the number of icons “CHANCE  70   c ” and “CHANCE  70   d ” displayed at the effect image display section  94 . In this case, three free games are executed for each icon “CHANCE”. While the free games are executed by the number of times corresponding to the number of icons “CHANCE”, a single icon “CHANCE  70   d ” is displayed in a blinking state so as to visualize the status in which the free games are certainly executed correspondingly to the number of symbols “CHANCE” that have been rearranged during the basic game. Where the free game is executed by all the corresponding number of times (three times in this case), the icon “CHANCE  70   d ” disappears. 
     Next, a process executed in the slot machine  10  according to the first embodiment, will be described in detail with reference to the drawings. The main CPU  41  controls the progress of a game by reading out and executing the game program. 
       FIG. 7  is a flowchart showing a subroutine of a main process. In the main process, first, when a power switch is turned on (that is, when power is supplied), a motherboard  40  and a gaming board  50  are activated respectively, so that the CPU  51  executes an initial setting process (step S 101 ). In this initial setting process, the main CPU  41  executes the BIOS stored in the ROM  42 , decompresses, in the RAM  43 , compressed data included in the BIOS, executes the BIOS decompressed in the RAM  43 , and performs diagnosis and initialization of each of the peripheral devices. The main CPU  41  writes game programs or the like from the ROM  42  into the RAM  43 , and retrieves data for setting a payout ratio and country-identification information. The main CPU  41  also performs an authentication process for each program during execution of the initial setting process. 
     Next, the main CPU  41  performs a game execution process described later with reference to  FIG. 8  (step S  102 ). In this game execution process, the main CPU  41  sequentially reads and executes the game programs or the like from the ROM  42 . By performing this game execution process, the slot machine according to the first embodiment  10  executes the game. The game execution process is repeatedly performed while power is supplied to the slot machine  10 . 
       FIG. 8  is a flowchart showing a subroutine of the game execution process invoked and performed at step S 102  of the subroutine shown in  FIG. 7 . First, the main CPU  41  judges whether a coin has been bet or not (step S 201 ). Specifically, the main CPU  41  judges whether or an input signal has been received. The input signal is output from the 1-BET switch  26 S at the time of operation of the 1-BET button  26  or output from the MAX-BET switch  27 S at the time of operation of the MAX-BET button  27 . The main CPU  41  controls the current step to return to the process at step S 201  upon judging that no coin has been bet (step S 201 : NO). 
     On the other hand, the main CPU  41  subtracts the number of bet coins from the credit amount stored in the RAM  43  (step S 202 ) upon judging that a coin has been bet (step S 201 : YES). Where the number of bet coins is larger than the credit amount stored in the RAM  43 , the main CPU  41  controls the current step to return to step S 101  without performing the process for subtracting the number of bet coins from the credit number stored in the RAM  43 . Where the number of bet coins exceeds the upper limit (50 coins in this embodiment) of coins that can be bet in one game, the main CPU  41  controls the step to return to step  203  without performing the process for subtracting the number of bet coins from the credit number stored in the RAM  43 . 
     At step S 203 , the main CPU  41  judges whether or not the start button  23  has been set to ON (step S 203 ). Specifically, the main CPU  41  judges whether or not an input signal output from the start switch  23 S at the time of pushing of the start button  23  has been received. The main CPU  41  controls the step to return to step  201  upon judging that the start button  23  has not been set to ON (step S 203 : NO). Where the start button  23  has not been set to ON (for example, where an instruction has been input to terminate the game without setting the start button  23  to ON), the main CPU  41  cancels acceptance of a subtraction result at step S 202 . 
     On the other hand, the main CPU  41  performs a symbol rearrangement process of the basic game (step S 204 ) upon judging that the start button  23  has been set to ON (step S 203 : YES). Specifically, the CPU  41  executes the program stored in the RAM  43  and determines the symbols to be rearranged in elements of the symbol matrix SM displayed on the lower image display panel  16 . The symbols are selected from among the symbols, “main character  121 ”, “sub character  122 ”, “office building  123 ”, “gold bullion  124 ”, “car  125 ”, “stock certificate  126 ”, “jet  127 ”, “villa  128 ”, and “CHANCE  70   a ”. This determination is based on the symbol weighting data and random numeric values sampled by sampling the random numeric values in a numerical range which comes under a predetermined range of random numeric values. The CPU  41  then rearranges the symbols in the elements of the symbol matrix SM. 
     Next, the main CPU  41  judges whether a prize has been established or not (step S 205 ). Specifically, the main CPU  41  judges whether or not the number of symbols of respective types rearranged in the elements of the symbol matrix SM is a winning number allowed to award any of payouts. Herein, the prize is established on condition that a predetermined number of symbols of the same type are rearranged in the elements of the symbol matrix SM. 
     Upon judging that the prize is established (step S 205 : YES), the main CPU  41  then performs a coin-payout process in accordance with the amount of bet and the number of coins set for the winning number (step S 206 ). Where the coins are deposited, the main CPU  41  performs a process for adding the number of paid-out coins to the credit amount stored in the RAM  43 . On the other hand, upon execution of the coin-payout process, the main CPU  41  pays out the predetermined number of coins by transmitting a control signal to the hopper  66 . 
     Meanwhile, the CPU  41  judges whether a free game trigger condition has been met or not (step S 207 ) when judging that the prize is not established (step S 205 : NO) or executing the process at step S 206 . Specifically, the main CPU  41  executes the program stored in the RAM  43  to sample the random numeric values in a numerical range which comes under a predetermined range of random numeric values, thereby judging whether or not the free game trigger condition has been met based on the sampled random numeric values. Upon judging that the free game trigger condition is met (step S 207 : YES), the main CPU  41  performs a free-game execution process described later with reference to  FIG. 11  (step S 208 ). In this free-game execution process, the main CPU  41  sequentially reads and executes the game programs or the like from the ROM  42  and performs the free-game execution process. 
     The CPU  41  terminates the game execution process when judging that the free game trigger condition is not met (step S 207 : NO) or when executing the process at step S 208 . 
       FIG. 9  is a flowchart showing a subroutine of a basic game symbol rearrangement process which is invoked and executed at step S 204  of the subroutine shown in  FIG. 8 . First, the main CPU  41  displays the symbols in a scrolling manner (step S 301 ). Specifically, the main CPU  41  successively displays in a scrolling manner the symbols that are rearranged in the elements of the symbol matrix SM displayed on the lower image display panel  16 . 
     Next, the main CPU  41  judges whether the side-BET or the MAX-BET has been set to ON or not (step S 302 ). Specifically, the main CPU  41  judges whether or not an input signal has been received, the signal being output from the side-BET switch  85 S when the side-BET button  85  is pressed, or being output from the MAX-BET switch  27 S when the MAX-BET button  27  is pressed. Upon judging that the side-BET or the MAX-BET has been set to ON (step S 302 : YES), the main CPU  41  performs a cumulative symbol rearrangement frequency determination process (step S 303 ). Specifically, the main CPU  41  determines an appearance frequency with which the symbol “CHANCE  70   a ” is rearranged, based on the program stored in the RAM  43 . This determination is made by performing a process for increasing the number of rearranged symbols “CHANCE  70   a ” correspondingly to the number of bet coins or the presence or absence of the side-BET, or by performing a process for widening a range of random numeric values set for rearrangement of the predetermined symbols in a case of using random numbers to determine a rearrangement frequency with which the symbols of respective types are rearranged. 
     The main CPU  41  then performs a process for determining symbols containing the cumulative symbols (step S 304 ). Specifically, the main CPU  41  reads out a storage area provided in the RAM  43 , the area storing data concerning the symbols. The main CPU  41  then determines a component ratio of respective symbols in a symbol group based on a rearrangement frequency of the symbol “CHANCE  70   a ” determined at step S 303 , random numeric values, and symbol weighting data. The random numeric values are sampled by sampling the random numeric values in a numerical range which comes under a predetermined range of random numeric values upon execution of the program stored in the RAM  43 . The symbol group contains the symbols, “main character  121 ”, “sub character  122 ”, “office building  123 ”, “gold bullion  124 ”, “car  125 ”, “stock certificate  126 ”, “jet  127 ”, and “villa  128 ”. This determination is based on the symbol weighting data and random numeric values sampled by sampling the random numeric values in a numerical range which comes under a predetermined range of random numeric values. 
     On the other hand, upon judging that the side-BET or the MAX-BET has not been set to ON (step S 304 : NO), the main CPU  41  performs a process for determining a symbol group not containing cumulative symbols (step S 305 ). Specifically, the main CPU  41  executes the program stored in the RAM  43  and determines a component ratio of respective symbols in a symbol group containing the symbols, “main character  121 ”, “sub character  122 ”, “office building  123 ”, “gold bullion  124 ”, “car  125 ”, “stock certificate  126 ”, “jet  127 ”, and “villa  128 ”. 
     Next, the main CPU  41  rearranges symbols (step S 306 ), Specifically, the main CPU  41  determines the symbols to be respectively rearranged in the elements of the symbol matrix SM, from the symbol group determined at step S 304  or S 305 . 
     The main CPU  41  then judges whether or not the cumulative symbol has been rearranged (step S 307 ). Specifically, in order to determine whether or not the symbols rearranged at step S 305  contain the cumulative symbol, the main CPU  41  judges whether a flag is set or not, which is stored in a frame memory region of each frame provided in the RAM  43  and indicates that the symbol “CHANCE  70   a ” serving as the cumulative symbol is currently displayed. Upon judging that the cumulative symbol has not been rearranged, the main CPU  41  terminates the basic game symbol rearrangement process (step S 307 : NO). 
     On the other hand, upon judging that the cumulative symbol has been rearranged (step S 307 : YES), the main CPU  41  performs a process for storing the number of cumulative symbols (step S 308 ). Specifically, the main CPU  41  adds the number of currently-displayed symbols “CHANCE  70   a ” serving as the cumulative symbol to the data that is stored in the RAM  43 , the data concerning the number of cumulative symbols having been rearranged during the free game. At the time of termination of this process, the basic game symbol rearrangement process is terminated. 
       FIG. 10  is a flowchart showing a subroutine of a free-game execution process invoked and executed at step S 208  of the subroutine shown in  FIG. 8 . First, the main CPU  41  judges whether or not the cumulative symbol exists (step S 401 ). Specifically, the main CPU  41  judges whether or not data stored in the RAM  43 , the data concerning the number of cumulative symbols, indicates one or more cumulative symbols. Upon judging that the cumulative symbol exists (step S 401 : YES), the main CPU  41  performs a process for setting the number of cumulative symbols to a free-game number T as the number of times in executing the free game (step S 404 ). Specifically, the main CPU  41  determines the free-game number T correspondingly to the data concerning the number of cumulative symbols, i.e., the cumulative symbol number data, which has been stored in the RAM. 
     Next, the main CPU  41  sets the free-game number B=T. Specifically, the main CPU  41  sets a remaining free-game number B=T in a storage area provided in the RAM  43 , the area storing the data indicative of the remaining free-game number B as the remaining number of times in executing the free game. T is the free-game number determined at step S 404 . 
     On the other hand, upon judging that the cumulative symbol does not exist (step S 401 : NO), the main CPU  41  performs a sub-game execution process (step S 402 ). Specifically, the main CPU  41  executes the program stored in the RAM  43  and determines a free-game number K, based on the execution result. 
     Next, the main CPU  41  performs a process for setting a free-game number B=K (step S 403 ). Specifically, the main CPU  41  sets a remaining free-game number B=K in a storage area provided in the RAM  43 , the area storing the data indicative of the remaining free-game number B. K is the free-game number determined at step S 402 . 
     Next, the main CPU  41  judges whether or not the start button  23  has been set to ON (step S 406 ). Specifically, the main CPU  41  judges whether or not an input signal has been received, the signal being output from the start switch  23 S when the start button  23  is pressed. The main CPU  41  controls the step to return to step S 406  upon judging that the start button  23  has not been set to ON (step S 406 : NO). 
     Upon judging that the start button  23  has been set to ON (step S 406 : YES), on the other hand, the main CPU  41  performs a process for displaying effect images (step S 407 ). Specifically, the main CPU  41  displays free-game-number display images  90   a  to  90   c  corresponding to the number of times in executing the free game on the upper image display panel  33  (see  FIGS. 6A and 6B ). 
     Next, the main CPU  41  performs a process for rearranging symbols in the free game (step S 408 ). Specifically, the CPU  41  executes the program stored in the RAM  43  and determines the symbols to be rearranged in the elements of the symbol matrix SM displayed on the lower image display panel  16 . The symbols are selected from among the symbols, “main character  121 ”, “sub character  122 ”, “office building  123 ”, “gold bullion  124 ”, “car  125 ”, “stock certificate  126 ”, “jet  127 ”, and “villa  128 ”. This determination is based on the symbol weighting data and random numeric values sampled by sampling the random numeric values in a numerical range which comes under a predetermined range of random numeric values. The main CPU  41  then rearranges the symbols to be arranged in the elements of the symbol matrix SM. 
     Next, the main CPU  41  judges whether or not a prize has been established (step S 409 ). Specifically, the main CPU  41  judges whether or not the number of symbols of respective types rearranged in the elements of the symbol matrix SM is a winning number allowed to award any of payouts. Herein, the prize is established on condition that a predetermined number of symbols of the same type are rearranged in the elements of the symbol matrix SM. 
     Thereafter, upon judging that the prize has been established (step S 409 : YES), the main CPU  41  performs a coin-payout process in accordance with the number of coins set for the winning number (step S 410 ). In a case where the coins are deposited, the main CPU  41  performs a process for adding the number of paid-out coins to the credit amount stored in the RAM  43 . Where the coins are paid out, the main CPU  41  pays out the predetermined number of coins by transmitting the control signal to the hopper  66 . 
     On the other hand, upon judging that the prize has not been established (step S 409 : NO) or upon executing the process at step S 410 , the main CPU  41  sets the remaining free-game number B=B−1 (step S 411 ). Specifically, the main CPU  41  sets B=B−1 at a value of the remaining free-game number B stored in the RAM  43 . 
     The main CPU  41  then judges whether or not a value of the remaining free-game number B is equal to zero (step S 412 ). Specifically, the main CPU  41  judges whether or not a value of the remaining free-game number B stored in the RAM  43  is equal to zero. Upon judging that the value of the remaining free-game number B is not zero (step S 412 : NO), the main CPU  41  controls the step to return to step S 406 . 
     On the other hand, upon judging that the value of B is equal to zero (step S 412 : YES), the main CPU  41  terminates the free-game execution process. 
       FIG. 11  shows a second embodiment of the present invention and is a flowchart showing a subroutine of the free-game execution process invoked and executed at step S 208  of the subroutine shown in  FIG. 8 . First, the main CPU  41  determines the free-game number T (step S 501 ). Specifically, the main CPU  41  determines the free-game number T in accordance with the program stored in the RAM 43 . 
     Next, the main CPU  41  judges whether or not the cumulative symbol exists (step S 502 ). Specifically, the main CPU  41  judges whether or not data stored in the RAM  43 , the data concerning the number of cumulative symbols, indicates one or more cumulative symbols. Upon judging that the cumulative symbol does not exist (step S 502 : NO), the main CPU  41  then judges whether a side-BET has been placed or not (step S 503 ). Specifically, the main CPU  41  judges whether a side-BET has been placed at or above a predetermined rate during the basic games intervened between the two nearest units of successive free games. Upon judging that the side-BET has been placed at or above a predetermined rate (step S 503 : YES), the main CPU  41  performs a sub-game execution process (step S 504 ). Specifically, the main CPU  41  executes a program related to the sub game, stored in the RAM  43 . 
     Next, the main CPU  41  determines the cumulative symbol number data based on an outcome of the sub game (step S 505 ). Specifically, the main CPU  41  determines the cumulative symbol number data corresponding to the outcome of the sub game stored in the RAM  43  and changes the cumulative symbol number data stored in the RAM  43 . 
     On the other hand, upon judging that the cumulative symbol exists (step S 502 : YES) or upon performing the process at step S 505 , the main CPU  41  performs a process for adding the number of cumulative symbols to the free-game number T (step S 506 ). Specifically, the main CPU 41  adds the cumulative symbol number data stored in the RAM  43  to the free-game number T. 
     Next, upon judging that the side-BET has not been placed at or above a predetermined rate (step S 503 : NO) or upon performing the process at step S 506 , the main CPU  41  performs a process for setting the free-game number B=T (step S 507 ). Specifically, the main CPU  41  sets a remaining free-game number B=T in a storage area of the data indicative of the remaining free-game number B provided in the RAM  43 . T is the free-game number determined at step S 501  and is an addition result when the number of cumulative symbols is added to T at step S 506 . 
     Next, the main CPU  41  judges whether or not the start button  23  has been set to ON (step S 508 ). Specifically, the main CPU  41  judges whether or not an input signal has been received, the signal being output from the start switch  23 S at the time of pushing of the start button  23 . The main CPU  41  controls the step to return to step S 508  upon judging that the start button  23  has not been set to ON (step S 508 : NO). 
     On the other hand, upon judging that the start button  23  has been set to ON (step S 508 : YES), the main CPU  41  performs a process for displaying effect images (step S 509 ). Specifically, the main CPU  41  displays the free-game-number display image  90   a  (see,  FIG. 6A ) corresponding to the number of times in executing the free game on the upper image display panel  33 . 
     The main CPU  41  performs a symbol rearrangement process of the free game (step S 510 ). Specifically, the CPU  41  executes the program stored in the RAM  43  and determines the symbols to be rearranged in the elements of the symbol matrix SM displayed on the lower image display panel  16 . These symbols are selected from among the symbols, “main character  121 ”, “sub character  122 ”, “office building  123 ”, “gold bullion  124 ”, “car  125 ”, “stock certificate  126 ”, “jet  127 ”, “villa  128 ”, and “CHANCE  70   a ”. This determination is based on the symbol weighting data and random numeric values sampled by sampling the random numeric values in a numerical range which comes under a predetermined range of random numeric values. The CPU  41  then rearranges the symbols in the elements of symbol matrix SM. 
     Next, the main CPU  41  judges whether or not a prize has been established (step S 511 ). Specifically, the main CPU  41  judges whether or not the number of symbols of respective types rearranged in the elements of the symbol matrix SM is a winning number allowed to award any of payouts. Herein, the prize is established on condition that a predetermined number of symbols of the same type are rearranged in the elements of the symbol matrix SM. 
     Thereafter, upon judging that the prize has not been established (step S 511 : YES), the main CPU  41  performs a coin-payout process for paying out the coins of the number set for the winning number (step S 512 ). In a case where the coins are deposited, the main CPU  41  performs a process for adding the number of paid-out coins to the credit amount stored in the RAM  43 . On the other hand, where the coins are paid out, the main CPU  41  pays out the predetermined number of coins by transmitting the control signal to the hopper  66 . 
     On the other hand, upon judging that the prize has not been established (step S 511 : NO) or upon executing the process at step S 512 , the main CPU  41  sets the remaining free-game number B=B−1 (step S 513 ). Specifically, the main CPU  41  sets B=B−1 at a value of the remaining free-game number B stored in the RAM  43 . 
     The main CPU  41  then judges whether or not a value of the remaining free-game number B is equal to zero (step S 514 ). Specifically, the main CPU  41  judges whether or not a value of the remaining free-game number B stored in the RAM  43  is equal to zero. Upon judging that the value of the remaining free-game number B is not zero (step S 514 : NO), the main CPU  41  controls the step to return to step S 508 . 
     On the other hand, upon judging that the value of B is equal to zero (step S 514 : YES), the main CPU  41  terminates the free-game execution process. 
     Next, a slot machine  100  according to a third embodiment will be described with reference to the drawings. The slot machine according to the third embodiment below is a so-called hybrid slot machine in which a plurality of rotatably-supported mechanical reels have a transparent liquid crystal panel on front surfaces to display images of various symbols drawn on peripheral surfaces of the mechanism reels through the transparent liquid crystal panel through which the pictures are allowed to pass. The slot machine according to the third embodiment has an appearance, circuitry, and the like that are substantially the same as those of the slot machine  10  according to the first embodiment. Thus, a duplicated explanation is omitted here. Constituent elements corresponding to those of the slot machine  10  are designated by the same reference numerals and are explained. 
       FIG. 12  is a view schematically showing an appearance of the slot machine according to the third embodiment. As shown in  FIG. 12 , the slot machine  100  is rotatably provided with five reels  101   a  to  101   e.  A symbol column made up of the symbols “main character  121 ”, “sub character  122 ”, “office building  123 ”, “gold bullion  124 ”, “car  125 ”, “stock certificate  126 ”, “jet  127 ”, “villa  128 ”, and “CHANCE  70   a ” is drawn on the respective one of the outer circumferential surfaces of the reels  101   a  to  101   e.    
     A main liquid crystal panel  202  formed of a transparent liquid crystal panel, which is disposed at the main door, is provided in front of the respective reels  101   a  to  101   e.  The main liquid crystal panel  202  displays the symbol display region  28  with visually recognizable rear surface so as to surround symbols displayed in the reels  101   a  to  101   e  in a stopped state, respectively. The symbols drawn on the reels  101   a  to  101   e  are visualized by rendering the symbol display region transparent. 
       FIGS. 13A and 13B  are views each showing an exemplary symbol matrix during the basic game according to the third embodiment. As shown in  FIGS. 13A and 13B , the symbol matrix SM is displayed on the main liquid crystal panel  202  provided at the slot machine  100  according to the present invention. A total of five reels  101   a  to  101   e  in five columns are rotatably provided rearwardly of the liquid crystal panel  202 . 
     As shown in  FIG. 13A , the five reels  101   a  to  101   e  are displayed in a stopped state during the basic game. The respective frames  103   a  to  103   o  of the symbol display region in the main liquid crystal panel  202  are transparently displayed so as to render these five reels  101   a  to  101   e  visually recognizable. In this case, with the use of the reels  101   a  to  101   e,  the symbols “main character  121 ”, “sub character  122 ”, “office building  123 ”, “gold bullion  124 ”, “car  125 ”, “stock certificate  126 ”, “jet  127 ”, and “villa  128 ” are displayed in a stopped state and the payout is determined based on the number of symbols of respective types that are displayed in a stopped state. 
     As shown in  FIG. 13B , the five reels  101   a  to  101   e  are displayed in a stopped state during the basic game. The respective frames  103   a  to  103   o  corresponding to the elements of the symbol matrix SM in the main liquid panel  202  are transparently displayed so as to render these five reels  101   a  to  101   e  visually recognizable. However, in a case, for example, where the basic game is started upon placing the side-BET or the MAX-BET, the symbol “CHANCE  70   a ” is occasionally displayed so as to cover the reel  101  in the symbol display region  28 . In this case, the reel  101   d  is displayed in a stopped state, displaying thereon the symbols “stock certificate  126 ”, “main character  121 ”, and “gold bullion  124  from top down. In this state, the symbol “CHANCE  70   a ” is displayed in the frame  103   k  of the symbol display region  28  so as to cover the symbol “main character  121 ” on the reel  101   d.  Then, the icon “CHANCE  70   c ” is displayed on the effect image display section  94  so as to indicate the number of the symbols “CHANCE  70   a ” that have been displayed during an interval between completion of the previous free game and start of the next free game. It should be noted that the displayed number of the icons “CHANCE  70   c ” is cumulatively increased every time the symbol “CHANCE  70   a ” is displayed. 
       FIG. 14  is a flowchart showing a subroutine of the basic game symbol rearrangement process according to the third embodiment invoked and executed at step S 204  of the subroutine in  FIG. 8 . First, the main CPU  41  displays the symbols in a scrolling manner (step S 601 ). Specifically, the main CPU  41  rotatably displays the five reels  101   a  to  101   e.    
     The main CPU  41  then rearranges the symbols (step S 602 ). Specifically, the CPU  41  executes the program stored in the RAM  43  and determines the symbols to be rearranged in the elements of the symbol matrix SM displayed on the lower image display panel  16 . The symbols are selected from among the symbols “main character  121 ”, “sub character  122 ”, “office building  123 ”, “gold bullion  124 ”, “car  125 ”, “stock certificate  126 ”, “jet  127 ”, and “villa  128 ”. This determination is based on the symbol weighting data and random numeric values sampled by sampling the random numeric values in a numerical range which comes under a predetermined range of random numeric values. The CPU  41  then rearranges the symbols by switching and displaying the reels  101   a  to  101   e  from a rotatable state into a stopped state. 
     Next, the main CPU  41  judges whether the side-BET or the MAX-BET has been set to ON (step S 603 ). Specifically, the main CPU  41  judges whether or not an input signal has been received, the signal being output from the side-BET switch  85 S when the side-BET button  85  is pressed, or alternatively, being output from the MAX-BET switch  27 S when the MAX-BET button  27  is pressed. Upon judging that the side-BET or the MAX-BET has not been set to ON (step S 603 : NO), the main CPU  41  terminates the symbol rearrangement process. 
     On the other hand, upon judging that the side-BET or the MAX-BET has been set to ON or not (step S 603 : YES), the main CPU  41  performs a process for judging whether or not display of the cumulative symbol has been determined (step S 604 ). Specifically, the main CPU  41  judges whether to display the cumulative symbol in the symbol display region  28  in accordance with the program provided in the RAM  43 . Upon judging that display of the cumulative symbol is not determined (step S 604 : NO), the main CPU  41  terminates the basic game symbol rearrangement process. 
     On the other hand, upon judging that display of the cumulative symbol is determined (step S 604 : YES), the main CPU  41  performs a process for displaying the cumulative symbol on the liquid crystal panel (step S 605 ). Specifically, the main CPU  41  displays the cumulative symbols, the number of which has been determined to be displayed at step S 604 , in any of the frames  103   a  to  103   o  of the symbol display region  28 . 
     Next, the main CPU  41  performs a process for storing the number of cumulative symbols (step S 606 ). Specifically, the main CPU  41  adds and stores the number of currently-displayed symbols “CHANCE  70   a ” serving as the cumulative symbol to the data stored in the RAM  43 . The number of currently-displayed symbols “CHANCE  70   a ” has been stored in a frame memory region of each frame provided in the RAM  43  while the data stored in the RAM  43  is relevant to the number of cumulative symbols having been rearranged during the free game. At the time of termination of this process, the symbol rearrangement process is terminated. 
     In the foregoing, while the embodiments of the present invention have been described, these embodiments merely present specific examples. An appropriate design change can be made for the specific configuration of each means or the like. Also, the effects described in the embodiments of the present invention are only listing the most preferable effects arising from the present invention, and the effects of the present invention are not limited to those described in the embodiments of the present invention.