Abstract:
A slot machine according to the present invention includes a display device having a symbol display region for displaying plural types of symbols; a memory for storing image data concerning the plural types of symbols; and a processor for controlling the display device and the memory. The plural types of symbols contain a plurality of symbol groups. Each of the symbol groups is made up of a plurality of step-up symbols. Each of the step-up symbols expresses a different added-value. The processor is programmed to: (a) read the image data concerning the plural types of symbols from the memory; (b) execute a game by processing the image data, the game for rearranging the plural types of symbols in the symbol display region; (c) rearrange at least the one or more symbols, in the case where the two or more symbols are rearranged in the symbol display region, in a predetermined period of time delay after previous symbol arrangement; and (d) exercise control to set the symbol rearranged in the predetermined period of time delay to a step-up symbol expressing an added-value higher than that of the previously-rearranged symbol, in the case where these symbols belong to the same symbol group.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority of U.S. Provisional Application No. 61/034,631 filed on Mar. 7, 2008. The contents of this application are incorporated herein by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a slot machine. 
         [0004]    2. Description of the Related Art 
         [0005]    Slot machines known as a type of gaming machines are constituted so as to: start games by players inserting credit into the gaming machine; rearrange columns of symbols in predetermined region of the gaming machine; and award payout based on a combination of rearranged symbols. In addition, the above slot machines are generally constituted to judge whether or not a precondition for payout has been 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 the 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. 
         [0006]    Therefore, layouts of arranged symbols or designs of payline are important factors in games, thereby becoming a focus of attention by providers or players of gaming machines. U.S. Pat. No. 6,896,615-B2 discloses an art in which the variety of payout is increased by arranging symbols after breaking elements in three rows and five columns of matrix display into more. 
         [0007]    On the other hand, in addition to mechanical reel-type slot machines, that have been conventionally mainstream, video reel-type slot machines provided with an electronic display screen are put into practical use, thereby increasing flexibility in expression or layout of symbols on the screen. Therefore, improvement in entertainability has been a challenge, which is to be achieved by adding visual expression to attract players&#39; interest to games beyond concepts of conventional simple layouts of symbols or designs of paylines. 
         [0008]    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 and a controlling method thereof by adding active expression to symbols arranged on a display of a slot machine. 
       SUMMARY OF THE INVENTION 
       [0009]    A first aspect of the present invention is a slot machine including a display device having a symbol display region for displaying plural types of symbols; a memory for storing image data concerning the plural types of symbols; and a processor for controlling the display device and the memory. The plural types of symbols contain a plurality of symbol groups. Each of the symbol groups is made up of a plurality of step-up symbols. Each of the step-up symbols expresses a different added-value. The processor is programmed to: (a) read the image data concerning the plural types of symbols from the memory; (b) execute a game by processing the image data, the game for rearranging the plural types of symbols in the symbol display region; (c) rearrange at least the one or more symbols, in the case where the two or more symbols are rearranged in the symbol display region, in a predetermined period of time delay after previous symbol arrangement; and (d) exercise control to set the symbol rearranged in the predetermined period of time delay to a step-up symbol expressing an added-value higher than that of the previously-rearranged symbol, in the case where these symbols belong to the same symbol group. 
         [0010]    According to the first aspect, a specific symbol is changed to express a higher value in accordance with a game progress. For example, in the case where the specific symbol is set to a bonus symbol, change of symbol allows players to play the game with expectations for bonus wining, thereby enhancing entertainability in symbol rearrangement. 
         [0011]    A second aspect of the present invention is a slot machine constituted as set fourth below. In the first aspect, the processor replaces the previously-rearranged symbol belonging to the same symbol group with the step-up symbol expressing the higher added-value, in the case where the step-up symbol expressing the higher added-value is rearranged in the itemized (d). 
         [0012]    According to the second aspect, the symbol expressing a higher value is arranged on the display device, which raises players&#39; expectations for prize wining, thereby enhancing entertainability in symbol rearrangement. 
         [0013]    A third aspect of the present invention is a slot machine constituted as set fourth below. In the first aspect, the processor exercises control in a manner to display an image of the step-up symbol in the case where the image of the step-up symbol is superimposed on an image of an adjacent symbol. 
         [0014]    According to the third aspect, in the case where an image of a specific symbol to be rearranged is larger than that of the regular symbol, the regular symbol is not displayed and the specific symbol is displayed in preference to the specific symbol. Therefore, the symbol expressing a higher added-value is displayed with emphasis, thereby further improving visual effects. 
         [0015]    A fourth aspect of the present invention is a slot machine constituted as set fourth below. In the first aspect, the processor awards a payout corresponding to the added-value of the step-up symbol rearranged in the itemized (d), in the case where a predetermined condition is met. 
         [0016]    According to the fourth aspect, the symbol on which players focus attention expresses the amount of winnable payout, thereby raising players&#39; expectations for prize. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1A  is a view showing an exemplary symbol matrix according to an embodiment of the present invention; 
           [0018]      FIG. 1B  is a view showing an exemplary symbol matrix according to the embodiment of the present invention; 
           [0019]      FIG. 1C  is a view showing an exemplary symbol matrix according to the embodiment of the present invention; 
           [0020]      FIG. 2  is a perspective view schematically showing a frame format of a slot machine according to the embodiment of the present invention; 
           [0021]      FIG. 3  is a view showing an internal construction of the slot machine shown in  FIG. 2 ; 
           [0022]      FIG. 4A  is a view showing an exemplary symbol matrix according to the embodiment of the present invention; 
           [0023]      FIG. 4B  is a view showing an exemplary symbol matrix according to the embodiment of the present invention; 
           [0024]      FIG. 5A  is a view showing an exemplary symbol matrix related to bonus award according to the embodiment of the present invention; 
           [0025]      FIG. 5B  is a view showing an exemplary symbol matrix related to the bonus award according to the embodiment of the present invention; 
           [0026]      FIG. 5C  is a view showing an exemplary symbol matrix related to the bonus award according to the embodiment of the present invention; 
           [0027]      FIG. 6A  is a view showing an exemplary symbol matrix related to the bonus award according to the embodiment of the present invention; 
           [0028]      FIG. 6B  is a view showing an exemplary symbol matrix related to the bonus award according to the embodiment of the present invention; 
           [0029]      FIG. 6C  is a view showing an exemplary symbol matrix related to the bonus award according to the embodiment of the present invention; 
           [0030]      FIG. 7  is a flowchart showing a subroutine of a main process according to the embodiment of the present invention; 
           [0031]      FIG. 8  is a flowchart showing a subroutine of a game execution process according to the embodiment of the present invention; 
           [0032]      FIG. 9  is a flowchart showing a subroutine of a symbol rearrangement process for the bonus award according to the embodiment of the present invention; and 
           [0033]      FIG. 10  is a flowchart showing a subroutine of the symbol rearrangement process for the bonus award according to the embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0034]    First, a slot machine  10  (see  FIG. 2 ) according to an embodiment of the present invention will be described with referring to the drawings. The slot machine according to the embodiment of the present invention 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 various images of symbols in a matrix form on the image display panel. The slot machine  10  according to the present invention executes two gaming modes alternately. The two gaming modes include a basic game and a free game. The basic game is executed upon consumption of inserted gaming values bet by players, namely, a credit. The free game is executed without consuming credits. Further, a bonus is awarded and a jackpot is won in the case where a bonus symbol is rearranged under a predetermined condition. As described later, symbols to be rearranged on the image display panel contains a plurality of symbol groups corresponding to types of bonus to be awarded, including a symbol group made up of a plurality of step-up symbols. Further, the step-up symbols are displayed so as to express different added-values, respectively. 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. 
         [0035]      FIGS. 1A to 1C  are views each showing an example case where symbols are rearranged in a symbol matrix SM (see  FIGS. 4A and 4B ) during a basic game according to the embodiment of the present invention. The symbol matrix SM is displayed on a lower image display panel  16  included in the slot machine  10  to be described later. The symbol matrix SM is made up of elements in five columns and three rows allowing symbols to be rearranged therein. The example cases shown in  FIGS. 1A to 1C  illustrate symbol rearrangement in the symbol matrix SM in the case where the bonus award is internally determined. As a precondition for a bonus award, the bonus to be paid out is a regular-size jackpot referred to as “MIN”. 
         [0036]    Each of the symbols “main character”  121   a,  “car”  125 , and “villa”  128  is rearranged on a first column in the symbol matrix SM shown in  FIG. 1A . The other columns display image effects in a scrolling manner. In this case, the symbol “main character”  121   a,  a symbol “briefcase”  121   c  shown in  FIG. 1B , and a symbol “bonus character”  121   e  are set to step-up symbols making up one symbol group. An added-value increases in order of the symbols  121   a,    121   c,  and  121   e.  A grade of the jackpot to be awarded is “MIN”, so that a group containing the symbol “bonus character”  121   e  is selected as a symbol group corresponding to a bonus. 
         [0037]    In  FIG. 1B , the symbols “briefcase”  121   c,  “office building”  123   a,  and “jet”  127  are rearranged on a second column, and third to fifth columns display image effects in a scrolling manner. Further, the symbol “main character”  121  a previously rearranged on the first column is replaced with the symbol “briefcase”  121   c.    
         [0038]    In  FIG. 1C , symbols “sub character”  122 , “office building”  123   a,  “gold bullion”  124   a,  “car”  125 , “stock certificate”  126 , “jet”  127 , “villa”  128 , and “bonus character”  121   e  are rearranged on the third to fifth columns. The previously-rearranged two symbols “briefcase”  121   c  shown in  FIG. 1B  are replaced with the symbols “bonus character”  121   e.  Rearrangement of the three symbols “bonus character”  121   e  ultimately determines the bonus award in terms of screen display. 
         [0039]    As described above, symbols are rearranged in stages on column-by-column basis at a predetermined time interval. Further, image effects that the bonus symbol “main character”  121   a  steps up are displayed. In this manner, the slot machine produces effects of appealing entertainability to players. 
         [0040]      FIG. 2  is a view schematically depicting a frame format of an appearance of the slot machine according to the embodiment of the present invention. 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. 
         [0041]    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 . 
         [0042]    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 symbol matrix SM in three rows and five columns. A single symbol is arranged in each of the elements of the symbol matrix SM, and the maximum of fifteen symbols can be displayed therein. 
         [0043]    A credit amount display section  31  of the lower image display panel  16  displays a by way of an image, credit corresponding to the number of inserted coins. A payout amount display unit  32  displays by way of an image, a combination of rearranged symbols or the number of coins to be paid if the predetermined number of symbols are rearranged. 
         [0044]    Provided on the lower side of the lower image display panel  16  at a center of the main door  13  is a control panel  20  on which a plurality of buttons  23  to  27  through which command regarding the process of the game is entered, a coin receiving slot  21  for receiving coins into the cabinet  11 , and bill validator  22  are disposed. 
         [0045]    On the control panel  20 , a start button  23 , a change button  24 , a cashout button  25 , a 1-BET button  26 , and a MAX-BET button  27  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 . 
         [0046]    The 1-BET button  26  is intended for entering a command for betting a credit corresponding to one coin. The MAX-BET button  27  is intended for entering a command for betting the maximum number (fifty in this embodiment) of coins that can be bet per game. Part of credit that is input through those input units is cumulatively stored in a predetermined memory region of the RAM  43  and a cumulative value is used as the reference to determine the amount of so-called jackpot in the case of bonus award. 
         [0047]    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. 
         [0048]    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. 
         [0049]    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 tickets, bar-codes having coded therein a variety of data including a credit amount, data and time, and an identification number of slot machine  10 . The printed tickets are output as bar-code-attached tickets  39 . A player causes another slot machine to read the bar-code-attached tickets  39 , allowing the slot machine to perform games, or alternatively, allowing the exchange of bar-code-attached tickets  39  with bills or the like at a predetermined site of a game facility (for example, at the casher in a casino). 
         [0050]    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 card 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. 
         [0051]      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 . 
         [0052]    The memory card  53  contains therein a nonvolatile memory 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 weighing 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 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. 
         [0053]    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 an 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 programs concerning a game progress. Furthermore, the game program includes image data or sound data to be output during the game. Furthermore, the game program includes image data or sound data to be output during the game. This image data includes image data concerning symbols rearranged in the symbol matrix SM, for example. 
         [0054]    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. Also, the IC socket  54 S is configured to allow the memory card  54  to be inserted thereinto or ejected therefrom, and is connected to a motherboard  40  through PCI bus. Accordingly, the GAL can be replaced with a replacement GAL  54  to change the payout-ratio setting data. 
         [0055]    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 with a commercially available general-purpose motherboard (a printed circuit board on which the essential parts of a personal computer are mounted). 
         [0056]    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 . 
         [0057]    The ROM  42  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. 
         [0058]    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. 
         [0059]    Both a main body PCB (Printed Circuit Board)  60  and a door PCB  80  are connected to the motherboard  40  by USB. A power supply unit  45  is also connected to the motherboard  40 . 
         [0060]    Equipment and devices, which generate input signals to be input to the main CPU 41 , and equipment and devices, operations of which are controlled by a control signal output from the main CPU 41 , are connected to the body PCB 60  and the door PCB 80 . The main CPU 41  executes the game programs stored in RAM  43 , based upon an input signal that was input to the main CPU 41 , thereby performing predetermined computational processing. Then, this CPU 41  stores results thereof into RAM 43 ; and transmits control signals to equipment and devices as control processing relative to the equipment and devices. 
         [0061]    Connected to the main body PCB  60  are a lamp  30 , a hopper  66 , a coin detecting section  67 , a graphic board  68 , a speaker  29 , a touch panel  69 , a bill validator  22 , a ticket printer  35 , a card reader  36 , a key switch  38 S, and a data display  37 . The lamp  30  illuminates in a predetermined pattern, based on a control signal output from a main CPU  41 . The lamp  30  is lit up in a predetermined pattern, based upon a control signal output from the main CPU 41 . 
         [0062]    The hopper  66  is installed in the cabinet  11 . This hopper pays out a predetermined number of coins from a coin payout exit  19  to a coin tray  18 , based upon a control signal output from the main CPU 41 . A coin detecting section  67  is installed inside the coin payout exit  19 . This detecting section outputs an input signal to the main CPU 41  at the time of detecting that a predetermined number of coins have been paid out from the coin payout exit  19 . 
         [0063]    The graphic board  68  performs control, based upon a control signal output from the main CPU 41 , over image display on the upper image display panel  33  and the lower image display panel  16 . The credit amount display section  31  (see  FIG. 2 ) on the lower image display panel  16  displays the amount of credits stored in the RAM 43 . Further, the payout amount display section  32  (see  FIG. 2 ) on the lower image display panel  16  displays the number of coins to be paid out. The graphic board  68  is equipped with: a VDP (Video Display Processor), which generates image data based upon a control signal output from the main CPU 41 ; and a video RAM, which temporarily stores image data generated by the VDP or the like. The image data used in generating the image data with VDP is contained in the game program read from the memory card  53  and stored in the RAM  43 . 
         [0064]    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 , upon accepting a legitimate bill, outputs an input signal to the main CPU  41  based on the bill amount. The main CPU  41  stores in the RAM  43  the credit amount corresponding to the bill amount transmitted by the input signal. 
         [0065]    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 upon 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 a player operates the key pad  38 . The data display  37  displays, based upon a control signal output from the main CPU 41 , the data read by the card reader  36  and the data input by a player through the key pad  38 . The control panel  20 , a reverter  21 S, a coin counter  21 C, and a cold cathode-ray tube  81  are connected to the door PCB 80 . 
         [0066]    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 ; and a MAX-BET switch  27 S corresponding to the MAX-BET button  27 . When the player operates the buttons  23  to  27 , the corresponding switches  23 S to  27 S output input signals to the main CPU  41 , respectively. 
         [0067]    The coin counter  21 C is provided inside the coin receiving slot  21 , and validates whether or not a coin inserted into the coin receiving slot  21  is legitimate. Those other than the legitimate coins are discharged from the coin payout exit  19 . The coin counter  21 C also outputs an input signal to the main CPU 41  when a legitimate coin is detected. 
         [0068]    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 . Specifically, when the hopper  66  is filled with coins, the reverter  21 S distributes legitimate coins into the hopper  21 S. 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 a 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 . 
         [0069]      FIGS. 4A to 6B  are views each showing an exemplary image displayed on the lower image display panel  16  of the slot machine  10  shown in  FIG. 2  according to the embodiment of the present invention.  FIGS. 4A and 4B  are views each showing an exemplary image displayed during the basic game in the slot machine shown in  FIG. 2 . 
         [0070]    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 display area section  92  is for displaying the symbol matrix SM. On both sides of the symbol matrix SM, the icons indicative of the number of coins that have been bet are arranged, and control is exercised to blink the icon corresponding to the bet amount. 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.    
         [0071]    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 paid out 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 amount of money is displayed at the charge display section  93   e.    
         [0072]    The effect image display section  94  displays effect images according to a type of the slot game. In other words, the effect image display section  94  displays different effect images between the basic and free games. 
         [0073]    Any of symbols, “main character”  121   a,  “sub character”  122 , “office building”  123   a,  “gold bullion”  124   a,  “car”  125 , “stock certificate”  126 , “jet”  127 , and “villa”  128  are rearranged in the symbol matrix SM displayed on the lower image display panel  16 . A payout is determined based on the number of these symbols displayed in the symbol matrix SM. 
         [0074]      FIG. 4A  is a view showing an example case where the symbols, “main character”  121   a,  “sub character”  122 , “office building”  123   a,  “gold bullion”  124   a,  “car”  125 , “stock certificate”  126 , “jet”  127 , and “villa”  128  are rearranged in the symbol matrix SM during the basic game. In  FIG. 4A , the two symbols “main character”  121  a are rearranged, the symbols being set to a trigger for switching the game from the basic game to the free game The condition to start the free game is met when the three or more symbols “main character”  121   a  are rearranged. This condition is not met in the above case, so that the basic game is continued without staring the free game. 
         [0075]      FIG. 4B  is a view showing an example case where symbols are rearranged in the symbol matrix SM during the basic game. In this case, the three symbols “gold bullion”  124   a  are rearranged in the symbol matrix SM. In the first embodiment of the present invention, a prize has been established when the three or more identical symbols are rearranged. In this case, coins are paid out, the number of which corresponds to a prize set for the symbol “gold bullion”  124   a  (see  FIG. 8 , step S 206 ). 
         [0076]      FIGS. 5A to 5C  are views each illustrating, likewise  FIGS. 1A to 1C , symbol rearrangement in the symbol matrix SM performed in the case where the bonus award is internally determined. In the case shown in  FIGS. 5A to 5C , a cumulative value of part of bet credit that is cumulatively stored in the RAM  43 , the value being referred to as a progressive value, reaches a predetermined value. Thus, ajackpot corresponding to “MAJOR” is paid out. 
         [0077]    In  FIG. 5A , each of the symbols “gold bullion”  124   a,  “car”  125 , and “villa”  128  is rearranged on the first column. The second to fifth columns display effect images in a scrolling manner. In this case, the symbol “gold bullion”  124   a  and a symbol “gold bullion tower”  124   e  shown in  FIG. 5B  are set to step-up symbols making up one symbol group. An added-value of the symbol  124   e  is higher than that of the symbol  124   a.  A grade of the jackpot to be awarded is “MAJOR”, so that a group containing the symbol “gold bullion tower”  124   e  is selected as a symbol group corresponding to a bonus. 
         [0078]    In  FIG. 5B , the symbols “main character”  121   a,  “office building”  123   a,  and “jet”  127  are rearranged on the second column while the symbol “gold bullion tower”  124   e  is rearranged on the third column. The fourth and fifth columns display effect images in a scrolling manner. The symbol “gold bullion”  124   a  previously rearranged on the first column is replaced with the symbol “gold bullion tower”  124   e.  The symbol “gold bullion tower”  124   e  is longitudinally extended, thereby being superimposed on each of the symbols “car”  125  and “villa”  128  that are previously rearranged on the first column. In this case, display is controlled so that the symbol “gold bullion tower”  124   e  as a step-up symbol is preferentially displayed. 
         [0079]    Next, in  FIG. 5C , the symbols “sub character”  122 , “car”  125 , and “stock certificate”  126  are rearranged on the fourth column and the symbol “gold bullion tower”  124   e  is rearranged on the fifth column. Rearrangement of the three symbols “gold bullion tower”  124   e  ultimately determines the bonus award corresponding to “MAJOR” in terms of screen display. 
         [0080]      FIGS. 6A to 6C  are views each illustrating, likewise  FIGS. 1A to 1C  and  5 A to  5 C, symbol rearrangement in the symbol matrix SM in the case where the bonus award is internally determined. In the case shown in  FIGS. 6A to 6C , a progressive value further increases, so that a jackpot corresponding to “MEGA” is to be paid out. 
         [0081]    In  FIG. 6A , each of the symbols “office building”  123   a,  “car”  125 , and “villa”  128  is rearranged on the first column. The second to fifth column display effect images in a scrolling manner. In this case, the symbol “office building”  123   a  and a symbol “tower”  123   e  shown in  FIG. 6B  are set to step-up symbols making up one symbol group. An added-value of the symbol “tower”  123   e  is higher than that of the symbol “office building”  123   a.  A grade of the jackpot to be awarded is “MEGA”, so that a group containing the symbol “tower”  123   e  is selected as a symbol group corresponding to a bonus. 
         [0082]    In  FIG. 6B , the symbols “main character”  121   a,  “sub character”  122 , and “jet”  127  are rearranged on the second column while the symbol “tower”  123   e  is rearranged on the third column. The fourth and fifth columns display effect images in a scrolling manner. The symbol “office building”  123   a  previously rearranged on the first column is replaced with the symbol “tower”  123   e.  The symbol “tower”  123   e  is set to a step-up symbol, thereby being controlled to be displayed in preference to each of the symbols “car”  125  and “villa”  128  that are previously rearranged on the first column. 
         [0083]    In  FIG. 6C , the symbols “sub character”  122 , “car”  125 , “stock certificate”  126  are rearranged on the fourth column while the symbol “tower” is rearranged on the fifth column. Rearrangement of the three symbols “tower”  123   e  ultimately determines the bonus award corresponding to “MEGA” in terms of screen display. 
         [0084]    Next, a process executed in the slot machine  10  according to the embodiment of the present invention, will be described in detail with reference to the drawings. The main CPU  41  controls the progress of a game by reading and executing the game program from the RAM  43 . 
         [0085]      FIG. 7  is a flowchart showing a subroutine of the 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 memory card  53  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. 
         [0086]    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 RAM 43 . By performing this game execution process, the slot machine  10  executes the game according to the embodiment of the present invention. The game execution process is repeatedly performed while power is supplied to the slot machine  10 . 
         [0087]      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 not 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). 
         [0088]    Next, 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). In the case 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 201  without performing the process for subtracting the number of bet coins from the credit amount stored in the RAM  43 . In the case where the number of bet coins exceeds the upper limit (fifty coins in this embodiment) of coins that can be bet in one game, the main CPU  41  controls the process to shift to step S 201  without performing the process for subtracting the number of bet coins from the credit amount stored in the RAM  43 . 
         [0089]    Next, 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 has been received, the signal being output from the start switch  23 S when the start button  23  is pushed. The main CPU  41  controls the step to return to step S 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 . 
         [0090]    On the other hand, the main CPU  41  performs a symbol rearrangement process (step S 204 ) upon judging that the start button  23  has been set to ON (step S 203 : YES). Specifically, the CPU  41  executes a program stored in the RAM  43  and samples a plurality of random numeric values corresponding to the symbol matrix SM from among predetermined random numbers. The CPU  41  then compares the sampled random numeric values to symbol weighting data which comes under a predetermined numerical range. The CPU  41  determines the symbol to be rearranged in the symbol matrix from among the symbols, “main character”  121   a,  “sub character”  122 , “office building”  123   a,  “gold bullion”  124   a,  “car”  125 , “stock certificate”  126 , “jet”  127 , “villa”  128 , and “blank” (see  FIG. 4A ). 
         [0091]    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 a combination of symbols rearranged in the symbol matrix SM results in a winning combination allowed to award any of payouts. Herein, the prize has been established on condition that the three or more symbols of the same type are rearranged in the symbol matrix SM (see  FIG. 4B ). 
         [0092]    Next, upon judging that the prize has been established (step S 205 : YES), the main CPU  41  performs a predetermined coin-payout process (step S 206 ). In the coin-payout process, the main CPU  41  transmits the control signal to the hopper  66  to pay out the predetermined amount of coins. The CPU  41  may control the process to add the credit corresponding to the coins to be paid out to the credit amount stored in the RAM  43 . 
         [0093]    Next, the CPU  41  judges whether a free game trigger has been established or not (step S 207 ) when judging that the prize is not established (step S 205 : NO) or after executing the payout process at step S 206 . Specifically, the main CPU  41  executes the program stored in the RAM  43  to sample the random numeric value corresponding to the symbol “main character”  121   a  from a numerical range which comes under a predetermined range of random numeric values, thereby judging whether or not the symbol “main character”  121   a  is rearranged based on the sampled random numeric values. The main CPU  41  then counts the number of the rearranged symbols “main character”  121   a  and judges that the free game trigger has been established when the three or more symbols “main character”  121   a  are rearranged. The main CPU  41  performs the free game execution process (step S 208 ) when judging that the free game trigger has been established (step S 207 : YES). In this free game execution process, the main CPU  41  reads and executes game programs or the like out of the RAM  43  in sequence, thereby executing the free game execution process. On the other hand, the main CPU  41  terminates the game execution process when judging that the free game is not established at step S 207  (step S 207 : NO) or when executing the process at step S 209 . 
         [0094]      FIG. 9  is a flowchart showing a subroutine of the symbol combining process invoked and performed at step S 303  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  executes the program stored in the RAM  43  to display effect images that are virtually recognized as if the symbols are scrolled at high speed in a downward direction of the columns of the symbol matrix. 
         [0095]    Next, the main CPU  41  judges whether the bonus has been established (step S 302 ), before rearranging symbols. Specifically, the main CPU  41  executes the program stored in the RAM  43  to sample the random numeric value corresponding to the predetermined bonus symbol from a numerical range which comes under a predetermined range of random numeric values, thereby determining based on the sampled random numeric value, the number of predetermined symbols that are rearranged in the symbol matrix SM. The main CPU  41  judges that the bonus has been established when determining the three or more bonus symbols are rearranged. 
         [0096]    Upon judging that the bonus has been established (step S 302 : YES), the main CPU  41  performs a process at step S 303 . Upon judging that the bonus has not been established (step S 302 : NO), the main CPU  41  executes a process at step S 304 . 
         [0097]    The main CPU  41  selects a symbol group corresponding to the established bonus, thereby stepping up and rearranging the corresponding symbol at every stop of rotation of columns (see  FIGS. 1A to 1C ,  5 A to  5 C,  6 A to  6 C, and  10 ). 
         [0098]    The main CPU  41  rearranges a regular symbol in the symbol matrix (step S 305 ). Specifically, the main CPU  41  executes the program stored in the RAM  43  to compare, from among a predetermined range of random numbers, a numeric value range determined based on each symbol weighting data to a random numeric value generated correspondingly to each element of the symbol matrix SM, thereby determining the symbol to be arranged in each element of the symbol matrix, from among the group of symbols selected at step S 303  or S 304 . 
         [0099]      FIG. 10  is a flowchart showing a subroutine of the symbol changing process invoked and performed at step S 303  of the subroutine shown in  FIG. 9 . First, the main CPU  41  reads a cumulative value of part of bet credit that is cumulatively stored in the RAM  43  from a predetermined memory region thereof, thereby determining the amount of bonus payout (step S 401 ). 
         [0100]    The main CPU  41  determines the bonus payout from among “MFN”, “MAJOR”, and “MEGA”, thereby selecting the corresponding symbol group (see  FIGS. 1A to 1C ,  5 A to  5 C, and  6 A to  6 C, step S 402 ). The main CPU  41  selects the symbol group containing the symbol “bonus character”  121   e  in the case of “MIN”, the symbol group containing the symbol “gold bullion tower”  124   e  in the case of “MAJOR”, and the symbol group containing the symbol “tower”  123   e  in the case of “MEGA” (see  FIGS. 1A to 1C ,  5 A to  5 C, and  6 A to  6 C). 
         [0101]    The main CPU  41  then judges whether or not the bonus symbol is arranged on the first column of the symbol matrix SM (step S 403 ). Specifically, the main CPU  41  judges whether or not the bonus symbol is arranged by referring to a random numeric value range assigned to the bonus symbol and random numeric value of the symbol determined to be rearranged on the first column. 
         [0102]    Upon judging that the bonus symbol is rearranged on the first column (step S 403 : YES), the main CPU  41  selects a symbol expressing the lowest added-value from among symbols belonging to the symbol group selected at the step S 402  and rearranges the selected symbol in matrix elements of the first column on which the bonus symbol is to be rearranged (see  FIGS. 1A ,  5 A, and  6 A, step S 405 ). On the other hand, upon judging that the bonus symbol is not rearranged on the first column (step S 403 : NO), the main CPU  41  rearranges a corresponding symbol from among the symbols “main character”  121   a,  “sub character”  122 , “office building”  123   a,  “gold bullion”  124   a,  “car”  125 , “stock certificate”  126 , “jet”  127 , and “villa”  128  that do not belong to the symbol group selected at step S 402  (step S 405 ). 
         [0103]    The main CPU  41  then judges whether or not the bonus symbol is arranged on the second column of the symbol matrix SM (step S 406 ). In the case of judging that the bonus group is rearranged on the second column (step S 406 : YES) on the condition that the symbol belonging to the symbol group selected at step S 402  is rearranged on the first column, the main CPU  41  selects the symbol expressing the higher added-value than that of the symbol rearranged on the first column (step S 407 ), thereby rearranging the selected symbol in the matrix element of the second column on which the bonus symbol is rearranged. On the other hand, where the bonus symbol is not rearranged on the first column, the main CPU  41  selects the symbol expressing the lowest added-value from among the symbols belonging to the symbol group selected at step S 402 , thereby rearranging the selected symbol (step S 408 ). 
         [0104]    In the case of judging that the bonus symbol is not rearranged on the second column (step S 406 : NO), the main CPU  41  rearranges a corresponding symbol from among the symbols “main character”  121   a,  “sub character”  122 , “office building”  123   a,  “gold bullion”  124   a,  “car”  125 , “stock certificate”  126 , “jet”  127 , and “villa”  128  that do not belong to the symbol group selected at step S 402  (see  FIGS. 5B and 6B , step S 408 ). 
         [0105]    Next, the main CPU  41  judges whether or not the bonus symbol is arranged on the third column of the symbol matrix SM (step S 409 ). In the case of judging that the bonus group is rearranged on the third column (step S 406 : YES) on the condition that the symbol belonging to the symbol group selected at step S 402  is rearranged on the first or second column, the main CPU  41  selects the symbol expressing the higher added-value than that of the previously-rearranged symbol (step S 410 ), thereby rearranging the selected symbol in the matrix element of the third column on which the bonus symbol is rearranged (see  FIGS. 5B and 6B , step S 411 ). On the other hand, where the bonus symbol is not rearranged on the first or second column, the main CPU  41  selects the symbol expressing the lowest added-value from among the symbols belonging to the symbol group selected at step S 402  (step S 410 ), thereby rearranging the selected symbol (step S 411 ). 
         [0106]    In the case of judging that the bonus symbol is not rearranged on the third column (step S 409 : NO), the main CPU  41  rearranges a corresponding symbol from among the symbols “main character”  121   a,  “sub character”  122 , “office building”  123   a,  “gold bullion”  124   a,  “car”  125 , “stock certificate”  126 , “jet”  127 , and “villa”  128  that do not belong to the symbol group selected at step S 402  (see  FIGS. 5B and 6B , step S 411 ). 
         [0107]    The main CPU  41  then judges whether or not the bonus symbol is arranged on the fourth column of the symbol matrix SM (step S 412 ) In the case of judging that the bonus group is rearranged on the fourth column (step S 412 : YES) on the condition that the symbol belonging to the symbol group selected at step S 402  is rearranged on the first, second, or third column, the main CPU  41  selects the symbol expressing the higher added-value than that of the previously-rearranged symbol (step S 413 ), thereby rearranging the selected symbol in the matrix element of the fourth column on which the bonus symbol is rearranged (step S 414 ). On the other hand, where the bonus symbol is not rearranged on the first, second, or third column, the main CPU  41  selects the symbol expressing the lowest added-value from among the symbols belonging to the symbol group selected at step S 402  (step S 413 ), thereby rearranging the selected symbol (step S 414 ). 
         [0108]    In the case of judging that the bonus symbol is not rearranged on the fourth column (step S 412 : NO), the main CPU  41  rearranges a corresponding symbol from among the symbols “main character”  121   a,  “sub character”  122 , “office building”  123   a,  “gold bullion”  124   a,  “car”  125 , “stock certificate”  126 , “jet”  127 , and “villa”  128  that do not belong to the symbol group selected at step S 402  (see  FIGS. 5B and 6B , step S 414 ). 
         [0109]    The main CPU  41  then judges whether or not the bonus symbol is arranged on the fifth column of the symbol matrix SM (step S 415 ). In the case of judging that the bonus group is rearranged on the fifth column (step S 415 : YES) on the condition that the symbol belonging to the symbol group selected at step S 402  is rearranged on the first, second, third, or fourth column, the main CPU  41  selects the symbol expressing the higher added-value than that of the previously-rearranged symbols (step S 416 ), thereby rearranging the selected symbol in the matrix element of the fifth column on which the bonus symbol is rearranged (step S 417 ). On the other hand, where the bonus symbol is not rearranged on the first, second, third, or fourth column, the main CPU  41  selects the symbol expressing the lowest added-value from among the symbols belonging to the symbol group selected at step S 402  (step S 416 ), thereby rearranging the selected symbol (step S 417 ) 
         [0110]    In the case of judging that the bonus symbol is not rearranged on the fifth column (step S 452 : NO), the main CPU  41  rearranges a corresponding symbol from among the symbols “main character”  121   a,  “sub character”  122 , “office building”  123   a,  “gold bullion”  124   a,  “car”  125 , “stock certificate”  126 , “jet”  127 , and “villa”  128  that do not belong to the symbol group selected at step S 402  (see  FIGS. 5B and 6B , step S 414 ). 
         [0111]    In the case where the step-up symbol in the symbol group selected at step S 402  is rearranged in the symbol changing process, and the previously-rearranged step-up symbols express the highest added-values among the symbol group, the symbol expressing the same highest added-value is rearranged later. In the case where the step-up symbols that are longitudinally extended (see  FIGS. 5B ,  5 C,  6 B, and  6 C) are mutually superimposed, the main CPU  41  exercises control so as to prevent superimposition of the symbols by changing positions of matrix elements in which the symbols are displayed. 
         [0112]    While the embodiment according to the present invention has been described, the description presents only some of the specific examples and is not intended to limit the present invention in any way and specific constructions of each means and the like can be properly changed in terms of design. Besides, the effects described in the embodiment of the present invention are only the most preferable effects generated from the present invention and the effects to be caused by the present invention is not limitative thereto.