Patent Publication Number: US-2009227328-A1

Title: Slot Machine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority of U.S. Provisional Application No. 61/033,932 filed on Mar. 5, 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 
     In a conventional slot machine, when a player inserts a game medium, such as a coin and a bill, in an insertion slot of a slot machine and presses a SPIN button, a display provided on a front face of a cabinet displays a plurality of symbols in a scrolling manner. Then, scrolling of each of the symbols automatically stops. 
     As such a slot machine, for example, as disclosed in U.S. Pat. No. 6,093,102, a slot machine exists which employs a concept of a winning line. In this concept, in case a combination of symbols rearranged on a winning line is a predetermined winning combination, a predetermined number of game media are paid out. 
     In addition, as such a slot machine, for example, as disclosed in each of U.S. Pat. No. 6,604,999 and U.S. Patent Publication No. 2002/0065124, a slot machine exists which provides two types of payouts, including a payout determined by a combination of symbols rearranged on a winning line and a payout determined by a number of displayed scatter symbols. 
     In the above-described conventional slot machine, a position of a winning line on which a winning combination is established or a displaying position of a scatter symbol is not related to a payout. Accordingly, a prolonged need exists for the advent of a slot machine which is capable of offering 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 rearrangement of the symbols. 
     SUMMARY OF THE INVENTION 
     A first aspect of the present invention is a slot machine including: a symbol matrix display area in which a plurality of symbols are arranged in column and row directions; a plurality of first reels provided corresponding to individual fields of the symbol matrix display area, the first reels having plural types of first symbols arranged thereon respectively; a plurality of second reels each having a larger diameter than that of each of the first reels, the plurality of second reels being disposed at outer peripheral sides of the plurality of first reels so as to enclose part of the plurality of first reels provided in a column direction, the plurality of second reels each having a plurality of second symbols arranged thereon, the second symbols being arranged in a superimposed manner on the first symbols on the first reels disposed in the symbol matrix display area; a plurality of first motors for driving the plurality of first reels, respectively, in a rotational manner; a second motor for driving the second reels in a rotational manner; and a processor for controlling rotation of the first and second reels by controlling the first and second motors. The plurality of first reels each have an independent rotation axis respectively. The second reels each have a rotation axis positioned closer to a rear side in comparison with that of each of the first reels when viewed from the symbol matrix display area. The processor is programmed to: (a) control rotation of the plurality of first reels to rearrange, in the symbol matrix display area, the first symbols arranged on the first reels; (b) control rotation of the second reels to rearrange, in the symbol matrix display area, the second symbols arranged on the second reels so as to superimpose the second symbols arranged on the second reels on the first symbols arranged on the first reels rearranged in the symbol matrix display area; and (c) award a prize in the case where a combination of the first symbols on the first reels rearranged in the symbol matrix display area and the second symbols on the second reels rearranged in a superimposed manner on the first symbols on the first reels is a winning combination on an activated line in a column, row, or diagonal direction. 
     According to the first aspect of the present invention, after the rearrangement of symbols, the symbols are further rearranged in a superimposed manner on the rearranged symbols. For example, in the case where the symbol “1Bar” is rearranged and then the symbol “3Bar” is rearranged thereon in a superimposed manner, a prize is to be awarded based on a payout corresponding to the symbol “3Bar”. Thus, the slot machine according to the first aspect raises players&#39; expectations for a payout, thereby enhancing entertainability in rearrangement of symbols. 
     A second aspect of the present invention is a slot machine constituted as set fourth below. In the first aspect, each of the second symbols arranged on the second reel is set to a WILD symbol. The processor, in the itemized (c), awards a prize according to a combination of the first symbols on the first reels disposed in the symbol matrix display area and the plurality of WILD symbols contiguously rearranged on any one of the second reels. 
     According to the second aspect, after rearrangement of symbols, symbols are further rearranged in a superimposed manner on the rearranged symbols. For example, after rearrangement of the symbols, the plurality of symbols “WILD” can be rearranged thereon in a superimposed manner. Thus, the slot machine according to the second aspect raises players&#39; expectations for a payout corresponding to the symbol “WILD”, thereby enhancing entertainability in rearrangement of symbols. 
     A third aspect of the present invention is a slot machine constituted as set fourth below. In the first aspect, the second reels each are made up of a predetermined symbol and a blank symbol. 
     According to the third aspect, after rearrangement of symbols, the symbols “WILD” are further rearranged in a superimposed manner on the rearranged symbols. For example, after rearrangement of symbols, the plurality of symbols “WILD” can be rearranged thereon in a superimposed manner. In this manner, the symbols “WILD” can be rearranged contiguously. Thus, the slot machine according to the third aspect raises players&#39; expectations for a payout corresponding to the symbol “WILD”, thereby enhancing entertainability in rearrangement of symbols. 
     A fourth aspect of the present invention is a slot machine constituted as set fourth below. In the first aspect, the processor is further programmed to: (d) execute a basic game; (e) execute a free game in the case where a predetermined condition is met during the basic game; and (f) execute processes in the itemized (a) to (c) during the free game. 
     According to the fourth aspect, after rearrangement of symbols during the free game, the symbols “WILD” are further rearranged in a superimposed manner on the rearranged symbols. For example, after rearrangement of the symbols during the free game, the plurality of symbols “WILD” can be rearranged thereon in a superimposed manner. In this manner, players can visually recognize the symbols “WILD” that are contiguously rearranged. Thus, the slot machine according to the fourth aspect raises players&#39; expectations for the free game, thereby enhancing entertainability in rearrangement of symbols. 
     A fifth aspect of the present invention is a slot machine including; a symbol matrix display area in which a plurality of symbols are arranged in column and row directions; a plurality of first reels provided corresponding to individual fields of the symbol matrix display area, the first reels having plural types of first symbols arranged thereon respectively; a plurality of second reels each having a larger diameter than that of each of the first reels, the plurality of second reels being disposed at outer peripheral sides of the plurality of first reels so as to enclose part of the plurality of first reels provided in a column direction, the plurality of second reels each having a plurality of second symbols arranged thereon, the second symbols being arranged in a superimposed manner on the first symbols on the first reels disposed in the symbol matrix display area; a plurality of first motors for driving the plurality of first reels, respectively, in a rotational manner; a second motor for driving the second reels in a rotational manner; and a processor for controlling rotation of the first and second reels by controlling the first and second motors. The plurality of first reels each have an independent rotation axis respectively. The second reels each have a rotation axis positioned closer to a rear side in comparison with that of each of the first reels when viewed from the symbol matrix display area. Each of the second symbols arranged on the second reels is set to a WILD symbol. The processor is programmed to: (a) control rotation of the plurality of first reels to rearrange the first symbols arranged on the first reels, in the symbol matrix display area,; (b) control rotation of the second reels to rearrange the second symbols arranged on the second reels, in the symbol matrix display area, so as to superimpose the second symbols arranged on the second reels on the first symbols arranged on the first reels rearranged in the symbol matrix display area; and (c) award a prize in the case where a combination of the first symbols on the first reels rearranged in the symbol matrix display area and the WILD symbols on the second reels rearranged in a superimposed manner on the first symbols arranged on the first reels is a winning combination on an activated line in a column, row, or diagonal direction. 
     According to the fifth aspect, after rearrangement of symbols, the symbols “WILD” are further rearranged on the rearranged symbols in a superimposed manner. For example, in the case where the symbol “1Bar” is rearranged and then the symbol “WILD” is rearranged thereon in a superimposed manner, a prize is to be awarded based on a payout corresponding to the symbol “WILD”. Thus, the slot machine according to the fifth aspect raises players&#39; expectations that the symbols “WILD” would be rearranged on the activated line, thereby enhancing entertainability in rearrangement of symbols. 
     A sixth aspect of the present invention is a slot machine constituted as set fourth below. In the fifth aspect, the second reels each are made up of a predetermined symbol and a blank symbol. 
     According to the sixth aspect, after rearrangement of symbols, the symbols “WILD” are further rearranged on the rearranged symbols in a superimposed manner. For example, after rearrangement of symbols, the plurality of symbols “WILD” is further rearranged on the rearranged symbols other than the symbols “WILD”, in a superimposed manner. In this manner, players can visually recognize the symbols “WILD” that are contiguously rearranged. Thus, the slot machine according to the sixth aspect raises players&#39; expectations for a payout corresponding to the symbol “WILD”, thereby enhancing entertainability in rearrangement of symbols. 
     A seventh aspect of the present invention is a slot machine constituted as set fourth below. In the fifth aspect, the processor is further programed to: (d) execute a basic game; (e) execute a free game in the case where a predetermined condition is met during the basic game; and (f) execute processes in the itemized (a) to (c) during the free game. 
     According to the seventh aspect, the symbols “WILD” are rearranged in a superimposed manner on the plurality of rearranged symbols during the free game. Thus, the slot machine according to the seventh aspect raises player&#39;s expectations that the symbols “WILD” would be rearranged on the activated line during the free game, thereby enhancing entertainability in rearrangement of symbols during the free game. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view showing one example of symbol-rearrangement according to a first embodiment; 
         FIG. 2  is a perspective view schematically showing a slot machine according to the first embodiment; 
         FIG. 3  is a perspective view schematically showing a reel according to the first embodiment; 
         FIG. 4  is a view showing an internal construction of the slot machine shown in  FIG. 2 ; 
         FIG. 5  is a view showing an internal construction of the reel shown in  FIG. 4 ; 
         FIG. 6A  is a view showing a correspondence relationship between various symbols and payouts at the time of a basic game according to the first embodiment; 
         FIG. 6B  is a view showing a correspondence relationship between the various symbols and payouts at the time of the basic game according to the first embodiment; 
         FIG. 7A  is a view showing one example of an image displayed in the slot machine shown in  FIG. 2  according to the first embodiment; 
         FIG. 7B  is a view showing one example of an image displayed in the slot machine shown in  FIG. 2  according to the first embodiment; 
         FIG. 8  is a flowchart showing a subroutine of main process according to the first embodiment; 
         FIG. 9  is a flowchart showing a subroutine of a game execution process according to the first embodiment; 
         FIG. 10  is a flowchart showing a subroutine of symbol rearrangement process according to the first embodiment; 
         FIG. 11  is a flowchart showing a subroutine of a game execution process according to a second embodiment; 
         FIG. 12  is a flowchart showing a subroutine of a free game execution process according to the second embodiment; 
         FIG. 13  is a flowchart showing a subroutine of a symbol rearrangement process during the free game according to the second embodiment; and 
         FIG. 14  is a view showing one example of an image displayed during the free game in the slot machine shown in  FIG. 2  according to the second embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First, a slot machine  10  according to a first embodiment will be described in detail with reference to the drawings. Here, the slot machine according to the first embodiment described below is a so-called hybrid type slot machine, which has a transparent liquid crystal panel allocated in front of a plurality of mechanical reels supported in a rotatable manner, and executes a game by displaying images of various symbols drawn on an outer peripheral surface of the mechanical reels through the transparent liquid crystal panel. 
       FIG. 1  is a view showing one example of rearranged symbols according to the first embodiment. As shown in  FIG. 1 , a total of fifteen reels  101   a  to  101   o  in five rows and three columns are provided in a rotatable manner in a symbol display area  28 . The reels  101   a  to  101   o  form a double-layered structure with level-up reels  102   a  to  102   e  that rotate outside the reels  101   a  to  101   o.  The level-up reels  102   a  to  102   e  each having a larger diameter than those of the reels  101   a  to  101   o  are disposed at outer peripheral sides of the reels  101   a  to  101   o.  The level-up reels  102   a  to  102   e  each disposed so as to enclose three of the reels  101   a  to  101   o  provided in a column direction are provided with level-up symbols (second symbols)  120  superimposed on symbols (first symbols) arranged on the reels  101   a  to  101   o.  In the symbol display area  28 , eight basic lines BL are set along the column and row directions. 
     In the embodiments of the present invention, in the symbol display area  28 , any of symbols “Blank”, “1Bar”, “2Bar, “3Bar”, “7”, and “WILD” is rearranged on the reels  101   a  to  101   o.  Symbols “Blank” or “WILD” are rearranged on the level-up reels  102   a  to  102   e  disposed at outer peripheral sides of the reels  101   a  to  101   o  in the column direction. A payout is awarded based on level-up symbols  120  rearranged in a superimposed manner on the above rearranged symbols. In this case, the symbols “7” are rearranged on the reels  101   a,    101   d,    101   g,    101   j.  The symbols “1Bar” are rearranged on the reel  101   b,    101   f,    101   h,    101   l,    101   o.  The symbols “Blank” are rearranged on the other reels. Next, when the level-up symbols  120  of “WILD” are rearranged in a superimposed manner on the reels  101   a,    101   b,    101   c,    101   h,    101   i,    101   m,    101   n,  by means of the level-up reels  102   a  to  102   e,  a payout corresponding to the symbols rearranged on the reels  101   a,    101   b,    101   c,    101   h,    101   i,    101   l,    101   m,    101   n,  are determined based on the symbols “WILD”. 
       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 . 
     A 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 to display various types of information or images such as effect images during the play of the game. 
     A symbol display area  28  for displaying symbols is provided at the center of the lower image display panel  16 . In the symbol display area  28 , nine display windows  103   a  to  103   o  are formed which allow a rear side thereof to be visually recognized. As shown in  FIG. 3 , fifteen reels  101   a  to  101   o  are rotatably provided. In addition, the reels  101   a  to  101   o  form a double-layered structure with the level-up reels  102   a  to  102   e  that rotate outside the reels  101   a  to  101   o.  The level-up reels  102   a  to  102   e  are each disposed so as to enclose three of the reels  101   a  to  101   o  provided in the column direction. The outside level-up reels  102   a  to  102   e  and the inside rotational reels  101   a  to  101   o  have independent rotational axes, respectively. The rotational axes of the level-up reels  102   a  to  102   e  are positioned closer to a rear side compared to those of the reels  101   a  to  101   o  when viewed from the symbol display area  28 . These axes are rotationally driven by means of separate motors. A symbol line made up of the symbols “Blank”, “1Bar”, “2Bar”, “3Bar”, “7”, and “WILD” is drawn on the outer peripheral surface of each of the reels  101   a  to  101   o.  On the other hand, a half periphery of each of the level-up reels  102   a  to  102   o  is transparent so that the reels  101   a  to  101   o  can be visually recognized. The remaining half perimeter has the level-up symbols made up of “Blank” and “WILD” drawn thereon in a manner that the symbols drawn on the reels  101   a  to  101   o  can be visually recognized. 
     In the lower image display panel  16 , six basic lines BL are set along the column or row directions of the symbol display area  28 . The basic lines BL serving as the winning lines specify combinations of symbols. 
     A credit amount display unit  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 coins to be paid if a predetermined combination of symbols are rearranged on the winning line. 
     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 , 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 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 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 lamp  30  and a speaker  29  are provided. On a lower side of the upper image display panel  33 , a ticket printer  35 , a card reader  36 , a data display  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 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 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. 4  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 . 
     A memory card  53  is composed of a non-volatile memory, such as CompactFlash (registered trademark), and stores a game program. The game program includes a symbol selection program. The symbol selection program is intended for determining symbols to be rearranged in the display windows  103   a  to  103   o  inside the symbol display area  28 . The symbol selection program includes symbol weighing data corresponding to each of a plurality of kinds of payout ratios (for example, 80%, 84%, and 88%). The symbol weighing data is indicative of the correspondence relationship between a code number of each of symbols and level-up symbols, and one or more random number values which come under a predetermined numerical range (0 to 256), with respect to each of the reels  101   a  to  101   o  and the level-up reels  102   a  to  102   e.  The payout ratio is determined according to the payout-ratio setting data output from the GAL  54 . The symbols to be stopped and displayed are determined depending upon the symbol weighing data corresponding to this payout ratio. 
     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 . 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 a program related to 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  41 , a ROM (Read Only Memory)  42 ; a RAM (Random Access Memory)  43 ; and a communication interface  44 . 
     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. 
     Connected to the main body PCB  60  are a lamp  30 , a reel controller  72 , 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 . 
     As shown in  FIG. 5 , a sub CPU  61  included in the reel controller  72  controls rotation and stop of the reels  101   a  to  101   o  and the level-up reels  102   a  to  102   e.  A motor driving circuit  62  including an FPGA (Field Programmable Gate Array)  63  and a driver  64  are connected to the sub CPU  61 . The FPGA  63  is an electronic circuit, such as a programmable LSI, and functions as a control circuit of stepping motors  70  and  71 . The driver  64  functions as an amplifier circuit of a pulse input to the stepping motors  70  and  71 . The motor driving circuit  62  is connected to stepping motors  70   a  to  70   o  that rotate the reels  101   a  to  101   p,  respectively, and stepping motors  90   a  to  90   e  that rotate the level-up reels  102   a  to  102   e,  respectively. The stepping motors  70  and  90  are stepping motors of one-two phase excitation mode. 
     In addition, an index detection circuit  65  and a position change detection circuit  71  are connected to the sub CPU  61 . The index detection circuit  65  detects positions (indices described later) of the reels  101   a  to  101   o  and the level-up reels  102   a  to  102   e  being rotated. Further, the index detection circuit  65  can detect loss of synchronization between the reels  101   a  to  101   o  and the level-up reels  102   a  to  102   e.    
     The position change detection circuit  71  detects change of positions where the reels  101   a  to  101   o  and the level-up reels  102   a  to  102   e  stop after rotation. For example, the position change detection circuit  71  detects change of positions where the reels  101   a  to  101   o  and the level-up reels  102   a  to  102   e  are stopped, in the case where a player forcibly changes the positions which actually do not result in a winning combination, to the positions corresponding to a winning combination. The position change detection circuit  71  is constituted so as to detect change of the positions of the reels  101   a  to  101   o  and the level-up reels  102   a  to  102   e  by detecting, for example, fins (not shown) mounted at predetermined intervals to an inner part of the reels  101   a  to  101   o  and the level-up reels  102   a  to  102   e.    
     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 (not shown) of the lower image display panel  16 . The number of coins to be paid out is displayed at a payout amount display section (not shown) 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 pad 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 . 
     A control panel  20 , a reverter  21 S, a coin counter  21 C, and a cold cathode tube  81  are connected to a 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. 
     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 . A 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 . 
       FIG. 6  is a view showing a correspondence relationship between each of various symbols and payouts. A table indicative of this correspondence relationship between various types of symbols and payouts is stored in the ROM  42  and is used to determine the payout. As shown in  FIG. 6A , where a predetermined symbol is rearranged on a winning line on which the player has bet, LIN payout is determined based on a winning combination. Furthermore, where the predetermined number of identical symbols are rearranged in the symbol display area  28 , as shown in  FIG. 6B , ANY payment is determined based on a winning combination. The LIN payout is obtained in the case where a winning combination appears as one of the combinations of symbols “7-7-7”, “3Bar-3Bar-3Bar”, “2Bar-2Bar-2Bar”, and “1Bar-1Bar-1Bar” on the basic line BL as the winning lines set in symbol display area. The ANY payout is obtained according to the number of symbols, “WILD”, “7”, “3Bar”, “2Bar”, and “1Bar”, which are rearranged in the symbol display area  28 . 
       FIGS. 7A and 7B  are views each showing one example of an image displayed in the slot machine shown in  FIG. 2  according to the first embodiment.  FIG. 7A  is a view showing one example of symbol rearrangement according to the first embodiment.  FIG. 7B  is a view showing one example of level-up symbol rearrangement according to the first embodiment. As shown in  FIG. 7A , the lower image display panel  16  is made up of display-related sections such as a display area section  92 , an information display section  93 , and an effect image display section  94 . The display area section  92  is for displaying a symbol matrix SM. In addition, the information display section  93  is arranged above the display area section  92 . This display section is made up of a credit amount display section  93   a,  a BET amount display section  93   b,  a character information display portion  93   c,  a PAID amount display section  93   d,  and a charge display section  93   e.    
     The number of coins presently credited is displayed at the credit amount display section  93   a  while the number of coins bet in 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 . The characters of “PLAYNOW” are displayed during the play of the game, whereas the characters of “GAMEOVER” are displayed at the intervals between the plays of the game. The number of coins that has 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. 
     At the effect image display section  94 , effect images in accordance with a type of the present slot game are displayed. Therefore, the effect image display section  94  displays effects images which are different depending on the basic and free games. 
     In the symbol display area  28  of the lower image display panel  16 , when the reels  101   a  to  101   o  are stopped, a total of fifteen symbols in three rows and five columns are rearranged in the display window  103 . In the display window  103 , any of the symbols “Blank”, “1Bar”, “2Bar”, “3Bar”, “7”, and “WILD” is rearranged. In this case, when the reels  101   a  to  101   o  are stopped, the symbols “7” are rearranged in the reels  101   a,    101   d,    101   g,    101   j;  the symbols “1Bar” are rearranged in the reels  101   b,    101   f,    101   h,    101   l,    101   o;  and the symbols “Blank” are rearranged in the other reels. 
     As shown in  FIG. 7B , after any of the symbols “Blank”, “1Bar”, “2Bar”, “3Bar”, “7”, and “WILD” is rearranged in the display windows  103  inside the symbol display area  28  of the lower image display panel  16 , the level-up reel  102   a  to  102   e  are stopped, and then, the level-up symbols  120  are rearranged. In this case, when the level-up symbol  120  of “WILD” are rearranged in a superimposed manner on the reels  101   a,    101   b,    101   c,    101   h,    101   i,    101   m,    101   n,  a payment is determined for the symbols rearranged on the reels  101   a,    101   b,    101   c,    101   h,    101   i,    101   m,  and  101   n,  based on the symbols “WILD”, so that a prize is awarded. 
     Next, a process executed in the slot machine  10  according to the first embodiment will be described in detail with reference to the accompanying drawings. The main CPU  41  reads out and executes a game program, thereby conducting the game. 
       FIG. 8  is a flowchart showing a subroutine of a main process. In the main process, when a power switch is turned on (that is, when power is supplied) first, a motherboard  40  and a gaming board  50  are activated respectively, and then, the CPU  51  executes an initial setting process (step S 101 ). In the initial setting process, the main CPU  41  executes a BIOS stored in the ROM  42  to decompress the compressed data incorporated in the BIOS to the RAM  43 , and executes the BIOS decompressed in the RAM  43 , and performs diagnosis and initialization of each of the peripheral devices. Further, the main CPU  41  writes game programs or the like from the ROM  42  into the RAM  43 , and acquires payout-ratio setting data 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. 9  (step S 102 ). In the game execution process, the main CPU  41  sequentially reads and executes game programs or the like from the ROM  42 . By performing the game execution process, the slot machine  10  executes the game according to the first embodiment. The game execution process is repeatedly performed while power is supplied to the slot machine  10 . 
       FIG. 9  is a flowchart showing a subroutine of the game execution process invoked and performed at step S 102  of the subroutine shown in  FIG. 8 . First, the main CPU  41  judges whether or not a coin has been bet (step S 201 ). Specifically, the main CPU  41  judges whether an input signal output from the 1-BET switch  26 S at the time of operation of the 1-BET button  26  has been received or whether an input signal output from the max BET switch  27 S at the time of operation of the max BET switch  27 S has been received. The main CPU  41  controls the current step to return to the process at the 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  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 201  without performing the process for subtracting (step S 202 ) 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, when the main CPU  41  judges that the start button  23  has been set to ON (step S 203 : YES), the main CPU  41  carries out symbol rearrangement process which will be described later with reference to  FIG. 10  (step S 204 ). Specifically, with respect to the symbols and the level-up symbols rearranged on the lower image display panel  16 , the CPU  41  executes a program stored in the RAM  43  to sample a random number value from a numerical value range of a predetermined random number value range. On the basis of the sampled random number value and symbol weighing data, the CPU  41  determines and rearranges the symbols “Blank”, “1Bar”, “2Bar”, “3Bar”, “7”, and “WILD”, and the level-up symbols “Blank” and “WILD”. 
     Next, the main CPU  41  judges whether a prize is established or not (step S 205 ). Specifically, the main CPU  41  judges whether or not a combination of symbols rearranged in the symbol display area  28  is a winning combination in which any payout is performed. In this case, the prize is established when a winning combination appears, the winning combination based on a combination of the symbols rearranged on the basic line BL as the winning line or based on the number of symbols rearranged in the symbol display area  28  (see  FIG. 6 ). 
     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 bet amount and the number of coins set for the winning combination (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 . 
     On the other hand, upon judging that the prize is not established (step S 205 : NO), or when the main CPU  41  executes the process of step S 206 , the main CPU  41  judges whether or not a bonus game trigger is established (step S 207 ). Specifically, the main CPU  41  executes a program stored in the RAM  43  to sample a random number value from a numerical value range of a predetermined random number value range. On the basis of the sampled random number value, the main CPU  41  judges whether or not the bonus game trigger is established. When the main CPU  41  judges that the bonus game trigger is established (step S 207 : YES), the main CPU  41  carries out a bonus game execution process (step S 208 ). In the bonus game execution process, the main CPU  41  sequentially reads and executes game programs or the like from the ROM  42  to carry out the bonus game execution process. 
     On the other hand, when the main CPU  41  judges that the bonus game trigger is not established (step S 207 : NO) or when the main CPU  41  executes the process in step S 208 , the main CPU  41  terminates the game execution process. 
       FIG. 10  is a flowchart showing a subroutine of the symbol rearrangement process invoked and executed in step S 204  of the subroutine shown in  FIG. 9 . First, the main CPU  41  displays symbols in the symbol display area  28  in a scrolling manner (step S 301 ). Specifically, the main CPU  41  starts rotation of the reels  101   a  to  101   o.  At this time, in the symbol display area  28 , six basic lines BL are set along the column or row direction. 
     Next, the main CPU  41  carries out a symbol determining process (step S 302 ). Specifically, with respect to symbols rearranged in the symbol display area  28 , the CPU  41  executes a program stored in the RAM  43  to sample a random number value from a numerical value range of a predetermined random number value range. On the basis of the sampled random number value and symbol weighing data, from among the symbols “Blank”, “1bar”, “2Bar”, “7”, and “WILD”, and the level-up symbols “Blank” and “WILD”, the CPU  41  determines those to be rearranged in the symbol display area  28 . 
     Next, the main CPU  41  carries out rearrangement of symbols (step S 303 ). Specifically, the main CPU  41  stops rotation of the reels  101   a  to  101   o  so as to display, in a stopped manner, the symbols determined at step S 302 , thereby rearranging the symbols (see  FIG. 7A ). 
     Next, the main CPU  41  stores the rearranged symbols (step S 304 ). Specifically, the main CPU  41  stores in the RAM  43  the symbols rearranged in the symbol display area  28  at step S 303 . 
     First, the main CPU  41  displays level-up symbols in the symbol display area  28  in a scrolling manner (step S 305 ). Specifically, the main CPU  41  starts rotation of the level-up reels  102   a  to  102   e.    
     Next, the main CPU  41  carries out rearrangement of level-up symbols (step S 306 ). Specifically, the main CPU  41  stops rotation of the level-up reels  103   a  to  103   e  so as to display, in a stopped manner, the level-up symbols determined at step S 302 , thereby rearranging the level-up symbols (see  FIG. 7B ). 
     Next, the main CPU  41  judges whether or not a payout of symbols is higher than that of previously arranged ones (step S 307 ). Specifically, the main CPU  41  judges whether or not a payout of the symbols stored in step S 304  is higher than that of level-up symbols after rearranged. When the main CPU  41  judges that the payout of the symbols is higher than that of the previously arranged ones (step S 307 : YES), the main CPU  41  determines a payout based on the level-up symbols (step S 308 ). For example, in the case where the level-up symbol  120  of “WILD” is rearranged on the symbol “1Bar” in a superimposed manner, a level of the symbol “1Bar” is increased to that of the symbol “WILD”, so that a payout that is to be awarded in the case where the symbol “WILD” is rearranged is determined (see  FIG. 7B ). The main CPU  41  terminates the symbol rearrangement process when executing the process in step S 308 . 
     On the other hand, when the main CPU  41  judges that a payout of the symbols is not higher than that of the previous one (step S 307 : NO), the main CPU  41  determines a payout based on the symbols (step S 309 ). For example, in case a combination of the symbols stored in step S 304  is a winning combination and the combination of the symbols is no longer a winning combination due to the level-up symbols rearranged at step S 306 , a payout is determined based on the winning combination of the symbols stored in step S 304 . The main CPU  41  terminates the symbol rearrangement process when executing the process in step S 309 . 
     Next, a slot machine  10  according to a second embodiment will be described with reference to the accompanying drawings. The slot machine according to the third embodiment below has an appearance, a circuit configuration, and the like that are substantially the same as those of the slot machine  10  according to the first embodiment of the present invention. Thus, a duplicated explanation is omitted hereinafter. In addition, the constituent elements corresponding to those of the slot machine  10  are designated by the same reference numerals and are explained. 
       FIG. 11  is a flowchart showing a subroutine of the game execution process according to the second embodiment, the process being invoked and performed at step S 102  of the subroutine shown in  FIG. 8 . First, the main CPU  41  judges whether or not a coin has been bet (step S 401 ). Specifically, the main CPU  41  judges whether an input signal output from the 1-BET switch  26 S at the time of operation of the 1-BET button  26  has been received or whether an input signal output from the max BET switch  27 S at the time of operation of the max BET switch  27  has been received. The main CPU  41  controls the current step to return to the process at the step S 401  upon judging that no coin has been bet (step S 401 : 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 402 ) upon judging that a coin has been bet (step S 401 : 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 401  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  403  without performing the process for subtracting the number of bet coins from the credit number stored in the RAM  43 . 
     At step S 403 , the main CPU  41  judges whether or not the start button  23  has been set to ON (step S 403 ). 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  401  upon judging that the start button  23  has not been set to ON (step S 403 : 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 402 . 
     On the other hand, the main CPU  41  performs a symbol rearrangement process of the basic game (step S 404 ) upon judging that the start button  23  has been set to ON (step S 403 : YES). Specifically, with respect to symbols and level-up symbols rearranged on the lower image display panel  16 , the CPU  41  executes a program stored in the RAM  43  to sample a random number value from a numerical value range of a predetermined random number value range. On the basis of the sampled random number value and symbol weighing data, the CPU  41  determines and rearranges the symbols “Blank”, “1Bar”, “2Bar”, “3Bar”, “7”, and “WILD”, and the level-up symbols “Blank” and “WILD”. 
     Next, the main CPU  41  judges whether or not a prize has been established (step S 405 ). Specifically, the main CPU  41  judges whether or not a combination of symbols rearranged in the symbol display area  28  is a winning combination in which any payout is performed. In this case, the prize is established when a winning combination appears, the winning combination based on a combination of the symbols rearranged on the basic line BL as the winning line or based on the number of symbols rearranged in the symbol display area  28  (see  FIG. 6 ). 
     Thereafter, upon judging that the prize has been established (step S 405 : YES), the main CPU  41  performs a coin-payout process in accordance with the bet amount and the number of coins set for the winning combination (step S 406 ). 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 . 
     On the other hand, the main CPU  41  judges whether a free game trigger has been established or not (step S 407 ) when judging that the prize has not been established (step S 405 : NO) or when executing the process at step S 406 . 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 satisfied based on the sampled random numeric values. Upon judging that the free game trigger is established (step S 407 : YES), the main CPU  41  performs a free-game execution process described later with reference to  FIG. 12  (step S 408 ). 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. 
     On the other hand, the CPU  41  terminates the game execution process when judging that the free game trigger is not established (step S 407 : NO) or when executing the process at step S 408 . 
       FIG. 12  is a flowchart showing a subroutine of a free-game execution process according to the second embodiment, the process being invoked and executed at step S 408  of the subroutine shown in  FIG. 11 . First, the main CPU  41  determines a free-game number T as a number of times in executing the free game (step S 501 ). Specifically, the main CPU  41  executes the program stored in the RAM  43 , thereby reading the number of times in executing the free game that is set in association with a random number using a random numeric value sampled in a numerical range which comes under a predetermined range of random numeric values 1 to 256. After that, the main CPU  41  determines the free-game number T. 
     Next, the main CPU  41  sets the free-game number B to T (step S 502 ). Specifically, the main CPU  41  sets B=T to a value of the remaining free-game number stored in a storage area of data indicative of the number of remaining games, the area being set in the RAM  43 . A value of T is equal to the free-game number T determined at step S 501 . 
     The main CPU  41  then judges whether the start button  23  has been set to ON or not (step S 503 ). 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 S 503  upon judging that the start button  23  has not been set to ON (step S 503 : NO). 
     Upon judging that the start button  23  has been set to ON (step S 503 : YES), the main CPU  41  performs a process for displaying effect images (step S 504 ). Specifically, the main CPU  41  displays a free-game-number display images  90   a  (see  FIG. 14 ) corresponding to the free-game number on the upper image display panel  33 . 
     Next, the main CPU  41  performs a symbol rearrangement process of the free game described later with reference to  FIG. 13  (step S 505 ). Specifically, the CPU  41  executes a program stored in the RAM  43  and determines the symbols to be rearranged in symbol matrix elements SM, from among the symbols “Blank”, “1Bar”, “2Bar”, “3Bar”, “7”, and “WILD”. 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 display windows  103   a  to  103   o  inside the symbol display area  28  displayed on the lower image display panel  16 . 
     Next, the main CPU  41  judges whether or not a prize has been established (step S 506 ). Specifically, the main CPU  41  judges whether or not a combination of symbols rearranged in the display windows  103  inside the symbol display area  28  is a winning combination in which any payout is performed. In this case, the prize is established when a winning combination appears, the winning combination based on a combination of the symbols rearranged on the basic line BL as the winning line or based on the number of symbols rearranged in the symbol display area  28  (see  FIG. 6 ). 
     Thereafter, upon judging that the prize has been established (step S 506 : YES), the main CPU  41  performs a coin-payout process in accordance with the bet amount and the number of coins set for the winning combination (step S 507 ). 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 . 
     On the other hand, upon judging that the prize has not been established (step S 506 : NO), or executing the process at step S 507 , the main CPU  41  sets the remaining free-game number B to B−1 (step S 508 ). Specifically, the main CPU  41  sets B=B−1 at a value of the free-game number B stored in the RAM  43 . 
     The main CPU  41  then judges whether the number of symbols “WILD” is equal to fifteen or not (step S 509 ). Specifically, the main CPU  41  judges whether or not the symbols “WILD” have been rearranged in all of the display windows  103   a  to  103   o  inside the symbol display area  28  (see  FIG. 14C ). Upon judging that the symbols “WILD” have been rearranged in all of the display windows  103   a  to  103   o  (step S 509 : YES), the main CPU  41  performs the coin-payout process in accordance with the bet amount and the number of coins set for the winning combination (step S 510 ). 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 . The main CPU  41  controls the current step to shift to the process at step S 512 . 
     On the other hand, upon judging that the number of symbols “WILD” is not equal to fifteen (step S 509 : NO), the main CPU  41  judges whether or not the remaining free-game number B is equal to zero (step S 511 ). Specifically, the main CPU  41  judges whether or not a value of the remaining game number 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 511 : NO), the main CPU  41  controls the step to return to step S 503 . On the other hand, upon executing the process at step S 510  or judging that a value of B is equal to zero (step S 511 : YES), the main CPU  41  performs a free-game termination process (step S 512 ). Specifically, the main CPU  41  terminates a control operation over the level-up reels at step S 607  in  FIG. 13  to be described later. The main CPU  41  terminates the free-game execution process when executing the process at step S 512 . 
       FIG. 13  is a flowchart showing a subroutine of the symbol rearrangement process of the free game according to the second embodiment, the process being invoked and executed at step S 505  of the subroutine shown in  FIG. 12 . First, the main CPU  41  displays symbols in the symbol display area  28  in a scrolling manner (step S 601 ). Specifically, the main CPU  41  starts rotation of the reels  101   a  to  101   o.  At this time, in the symbol display area  28 , six basic lines BL are set along the column or row direction. 
     Next, the main CPU  41  carries out a symbol determination process (step S 602 ). Specifically, with respect to symbols rearranged in the symbol display area  28 , the CPU  41  executes a program stored in the RAM  43  to sample a random number value from a numerical value range of a predetermined random number value range. On the basis of the sampled random number value and symbol weighing data, from among the symbols “Blank”, “1Bar”, “2Bar”, “3Bar”, “7”, and “WILD”, and the level-up symbols “Blank” and “WILD”, the CPU  41  determines those to be rearranged in the symbol display area  28 . 
     Next, the main CPU  41  carries out rearrangement of symbols (step S 603 ). Specifically, the main CPU  41  stops rotation of the reels  101   a  to  101   o  so as to display, in a stopped state, the symbols determined at step S 602 , thereby rearranging the symbols. 
     Next, the main CPU  41  displays level-up symbols in the symbol display area  28  in a scrolling manner (step S 604 ). Specifically, the main CPU  41  starts rotation of the level-up reels  102   a  to  102   e.    
     Next, the main CPU  41  carries out rearrangement of level-up symbols (step S 605 ). Specifically, the main CPU  41  stops rotation of the level-up reels  103   a  to  103   e  so as to display, in a stopped state, the level-up symbols determined at step S 602 , thereby rearranging level-up symbols (see  FIG. 14B ). 
     The main CPU  41  then judges whether or not the number of symbols “WILD” on the basic line in a column direction is equal to three (step S 606 ). Specifically, the main CPU  41  judges whether or not three of the level-up symbols “WILD” are rearranged in the level-up reel  103   a  to  103   e  in a column direction. Upon judging that the number of symbols “WILD” rearranged in a column direction is not equal to three (step S 606 : NO), the main CPU  41  terminates the free-game symbol rearrangement process when the process at step S 606  is executed. 
     On the other hand, upon judging that the number of symbols “WILD” rearranged in a column direction is equal to three (step S 606 : YES), the main CPU  41  controls the level-up reels (step S 607 ). Specifically, the main CPU  41  controls the level-up reels  103   a  to  103   e  in a manner to stop rotation of the level-up reels  103  having three of the level-up symbols  120  of “WILD” rearranged thereon, on the basic line in a column direction during the free game. The main CPU  41  terminates the free-game symbol rearrangement process when executing the process at step S 607  (see  FIG. 14C ). 
       FIGS. 14A ,  14 B, and  14 C are views each showing one example of an image displayed during the free game in the slot machine shown in  FIG. 2  according to the second embodiment. As shown in  FIG. 14A , upon start of the free game, the upper image display panel  33  displays the free-game-number display image  90   a  indicative of the number of times in executing the free game. In this case, the free-game-number display image  90   a  of “10 FREE GAME” is displayed indicating that the number of times in executing the free game has been set to ten. 
     As shown in  FIG. 14B , after any of the symbols “Blank”, “1Bar”, “2Bar”, “3Bar”, “7”, and “WILD” is rearranged in any of the display windows  103  inside the symbol display area  28  of the lower image display panel  16 , rotation of the level-up reels  102   a  to  102   e  is stopped, and then the level-up symbols are rearranged. In this case, when the level-up symbols  120  of “WILD” are rearranged in a superimposed manner on the reels  101  in the display windows  103   a,    103   b,    103   c,    103   g,    103   h,    103   i,    103   m,    103   n,  three of the symbols “WILD” are rearranged on each of the level-up reels  102   a  and  102   c  in a column direction. Therefore, rotation of the level-up reels  102   a  and  102   c  is stopped during the free game in which the symbols “WILD” are contiguously rearranged. 
     As shown in  FIG. 14C , in the case where fifteen of the symbols “WILD” and the level-up symbol  120  of “WILD” are rearranged in the display windows  103   a  to  103   o  inside the lower image display panel  16 , the main CPU  41  terminates the free game and determines a payout that corresponds to a winning combination of the symbols “WILD” (see  FIG. 6 ). 
     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.