Tutorial gomoku

This tutorial will guide you through the basics of creating a simple game on BGA Studio, through the example of Gomoku (also known as Gobang or Five in a Row).

You will start from our 'empty game' template

Here is how your games looks by default when it has just been created:

Set up the board

Gather useful images for the game and edit them as needed. Upload them in the 'img' folder of your SFTP access.

Edit gomoku.js (replace gomoku by your game name) to add the divs for your board at the beginning of the setup function:

document.getElementById('game_play_area').insertAdjacentHTML('beforeend', `
<div id="gmk_game_area">
	<div id="gmk_background">
		<div id="gmk_goban">
		</div>
	</div>	
</div>
`);

Edit .css to set the div sizes and positions and show the image of the board as background.

#gmk_game_area {
	text-align: center;
	position: relative;
}

#gmk_background {
	width: 620px;
	height: 620px;	
	position: relative;
	display: inline-block;
}

#gmk_goban {	
	background-image: url( 'img/Goban.jpg');
	width: 620px;
	height: 620px;
	position: absolute;	
}

You can find the goban board image here : https://en.doc.boardgamearena.com/File:Goban.jpg

Set up the backbone of your game

Edit dbmodel.sql to create a table for intersections. We need coordinates for each intersection and a field to store the color of the stone on this intersection (if any).

CREATE TABLE IF NOT EXISTS `intersection` (
   `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
   `coord_x` tinyint(2) unsigned NOT NULL,
   `coord_y` tinyint(2) unsigned NOT NULL,
   `stone_color` varchar(8) NULL,
   PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;

Edit Game.php->setupNewGame() (in the modules/php dir) to insert the empty intersections (19x19) with coordinates into the database.

        // Insert (empty) intersections into database
        $sql = "INSERT INTO intersection (coord_x, coord_y) VALUES ";
        $values = array();
        for ($x = 0; $x < 19; $x++) {
            for ($y = 0; $y < 19; $y++) {
        	
            	$values[] = "($x, $y)";   	
            }
        }
        $sql .= implode( ',', $values );
        $this->DbQuery( $sql );

Edit Game.php->getAllDatas() to retrieve the state of the intersections from the database.

        // Intersections
        $sql = "SELECT id, coord_x, coord_y, stone_color FROM intersection ";
        $result['intersections'] = $this->getCollectionFromDb( $sql );

Edit .js to create the function to generate intersections.

addIntersection: function(x, y, stone_color) {
            const stone_type = stone_color == null ? 'empty' : stone_color;
            document.getElementById('gmk_background').insertAdjacentHTML('beforeend', `<div class="gmk_intersection" data-color="${stone_type}" id="intersection_${x}_${y}"></div>`);
        },  

Define the styles for the intersection divs.

.gmk_intersection {
    width: 30px;
    height: 30px;
    position: relative;
}

Edit .js->setup() to setup the intersections layer that will be used to get click events and to display the stones. The data you returned in $result['intersections'] in Game.php->getAllDatas() is now available in your .js->setup() in gamedatas.intersections.

            // Setup intersections
            for( var id in gamedatas.intersections )
            {
                var intersection = gamedatas.intersections[id];

                this.addIntersection(intersection.coord_x, intersection.coord_y, intersection.stone_color);

                var x_pix = this.getXPixelCoordinates(intersection.coord_x);
                var y_pix = this.getYPixelCoordinates(intersection.coord_y);
                
                this.slideToObjectPos( $('intersection_'+intersection.coord_x+'_'+intersection.coord_y), $('gmk_background'), x_pix, y_pix, 10 ).play();

                if (intersection.stone_color != null) {
                    // This intersection is taken, it shouldn't appear as clickable anymore
                    document.getElementById('intersection_' + intersection.coord_x + '_' + intersection.coord_y).classList.remove('clickable');
                }
            } 

Use some temporary css border-color or background-color and opacity to see the divs and make sure you have them positioned right.

.gmk_intersection {
    width: 30px;
    height: 30px;
    position: relative;
    background-color: blue;
    opacity: 0.3;
}

You can declare some constants on top of your .js for easy repositioning

const INTERSECTION_WIDTH = 30;
const INTERSECTION_HEIGHT = 30;		
const INTERSECTION_X_SPACER = 3;
const INTERSECTION_Y_SPACER = 3;
const X_ORIGIN = 10;
const Y_ORIGIN = 10;

• Then use it in your getXPixelCoordinates and getYPixelCoordinates functions

        getXPixelCoordinates: function( intersection_x )
        {
        	return X_ORIGIN + intersection_x * (INTERSECTION_WIDTH + INTERSECTION_X_SPACER); 
        },
        
        getYPixelCoordinates: function( intersection_y )
        {
        	return Y_ORIGIN + intersection_y * (INTERSECTION_HEIGHT + INTERSECTION_Y_SPACER); 
        },

Here is what you should get:

Manage states and events

Define your game states in states.inc.php. For gomoku we will use 3 states in addition of the predefined states 1 (gameSetup) and 99 (gameEnd). One to play, one to check the end game condition, one to give his turn to the other player if the game is not over.

The first state requires an action from the player, so its type is 'activeplayer'.

The two others are automatic actions for the game, so their type is 'game'.

We will update the progression while checking for the end of the game, so for this state we set the 'updateGameProgression' flag to true.

    2 => array(
        "name" => "playerTurn",
        "description" => clienttranslate('${actplayer} must play a stone'),
        "descriptionmyturn" => clienttranslate('${you} must play a stone'),
        "type" => "activeplayer",
        "possibleactions" => array( "actPlayStone" ),
        "transitions" => array( "stonePlayed" => 3, "zombiePass" => 3 )
    ),

    3 => array(
        "name" => "checkEndOfGame",
        "description" => '',
        "type" => "game",
        "action" => "stCheckEndOfGame",
        "updateGameProgression" => true,
        "transitions" => array( "gameEnded" => 99, "notEndedYet" => 4 )
    ),

    4 => array(
        "name" => "nextPlayer",
        "description" => '',
        "type" => "game",
        "action" => "stNextPlayer",
        "transitions" => array( "" => 2 )
    ),

Implement the 'stNextPlayer()' function in Game.php to manage turn rotation. Except if there are special rules for the game turn depending on context, this is really easy:

    function stNextPlayer()
    {
    	$this->trace( "stNextPlayer" );
    	 
    	// Go to next player
    	$active_player = $this->activeNextPlayer();
    	$this->giveExtraTime( $active_player );    
    	 
    	$this->gamestate->nextState();
    }

Implement the 'stCheckEndOfGame()' function in Game.php to manage the state 3. The real implementation will be exposed later, but for now just create it to be able to run the game:

    function stCheckEndOfGame()
    {
        $this->trace('stCheckEndOfGame');

        $this->gamestate->nextState('notEndedYet');
    }

Add onclick events on intersections in .js->setup()

           // Add events on active elements (the third parameter is the method that will be called when the event defined by the second parameter happens - this method must be declared beforehand)
           this.addEventToClass( "gmk_intersection", "onclick", "onClickIntersection");

Declare the corresponding .js->onClickIntersection() function, which calls an action function on the server with appropriate parameters.

        onClickIntersection: function( evt )
        {
            console.log( '$$$$ Event : onClickIntersection' );
            dojo.stopEvent( evt );

            if( ! this.checkAction( 'actPlayStone' ) )
            { return; }

            var node = evt.currentTarget.id;
            var coord_x = node.split('_')[1];
            var coord_y = node.split('_')[2];
            
            console.log( '$$$$ Selected intersection : (' + coord_x + ', ' + coord_y + ')' );
            
            if ( this.isCurrentPlayerActive() ) {
                this.bgaPerformAction('actPlayStone', { coord_x: coord_x, coord_y: coord_y });
            }
        },

Add game action in Game.php to update the database, send a notification to the client providing the event notified (‘stonePlayed’) and its parameters, and proceed to the next state.

    function actPlayStone(int $coord_x, int $coord_y)
    {        
        $player_id = $this->getActivePlayerId();
        
        // Check that this intersection is free
        $sql = "SELECT
                    id, coord_x, coord_y, stone_color
                FROM
                    intersection 
                WHERE 
                    coord_x = $coord_x 
                    AND coord_y = $coord_y
                    AND stone_color is null
               ";
        $intersection = $this->getObjectFromDb( $sql );

        if ($intersection == null) {
            throw new \BgaUserException( $this->_("There is already a stone on this intersection, you can't play there") );
        }

        // Get player color
        $sql = "SELECT
                    player_id, player_color
                FROM
                    player 
                WHERE 
                    player_id = $player_id
               ";
        $player = $this->getNonEmptyObjectFromDb( $sql );
        $color = ($player['player_color'] == 'ffffff' ? 'white' : 'black');

        // Update the intersection with a stone of the appropriate color
        $intersection_id = $intersection['id'];
        $sql = "UPDATE
                    intersection
                SET
                    stone_color = '$color'
                WHERE 
                    id = $intersection_id
               ";
        $this->DbQuery($sql);
        
        // Notify all players
        $this->notifyAllPlayers( "stonePlayed", clienttranslate( '${player_name} dropped a stone on ${coord_x},${coord_y}' ), array(
            'player_id' => $player_id,
            'player_name' => $this->getActivePlayerName(),
            'coord_x' => $coord_x,
            'coord_y' => $coord_y,
            'color' => $color
        ) );

        // Go to next game state
        $this->gamestate->nextState( "stonePlayed" );
    }

Catch the notification in .js->setupNotifications() and link it to a javascript function to execute when the notification is received.

        setupNotifications: function()
        {
            console.log( 'notifications subscriptions setup' );
        
            const notifs = [
                ['stonePlayed', 1],
            ];
    
            notifs.forEach((notif) => {
                dojo.subscribe(notif[0], this, `notif_${notif[0]}`);
                this.notifqueue.setSynchronous(notif[0], notif[1]);
            });
        }

Implement this function in javascript to update the intersection to show the stone, and register it inside the setNotifications function.

        notif_stonePlayed: function( notif )
        {
	    console.log( '**** Notification : stonePlayed' );
            console.log( notif );

            // Create a stone
            document.getElementById( 'intersection_' + notif.args.coord_x + '_' + notif.args.coord_y ).insertAdjacentHTML('beforeend', `<div class="gmk_stone" data-color="${notif.args.color}" id="stone_${notif.args.coord_x}_${notif.args.coord_y}"></div>`);

            // Place it on the player panel
            this.placeOnObject( $( 'stone_' + notif.args.coord_x + '_' + notif.args.coord_y ), $( 'player_board_' + notif.args.player_id ) );

            // Animate a slide from the player panel to the intersection
            dojo.style( 'stone_' + notif.args.coord_x + '_' + notif.args.coord_y, 'zIndex', 1 );
            var slide = this.slideToObject( $( 'stone_' + notif.args.coord_x + '_' + notif.args.coord_y ), $( 'intersection_' + notif.args.coord_x + '_' + notif.args.coord_y ), 1000 );
            dojo.connect( slide, 'onEnd', this, dojo.hitch( this, function() {
                        // At the end of the slide, update the intersection 
                        document.getElementById( 'intersection_' + notif.args.coord_x + '_' + notif.args.coord_y).dataset.color = notif.args.color;
                        dojo.removeClass( 'intersection_' + notif.args.coord_x + '_' + notif.args.coord_y, 'clickable' );
        			
                        // We can now destroy the stone since it is now visible through the change in style of the intersection
                        dojo.destroy( 'stone_' + notif.args.coord_x + '_' + notif.args.coord_y );
       	    }));
            slide.play();
        },

For this function to work properly, you also need to define the css styles for the stones

.gmk_intersection, .gmk_stone  {
	width: 30px;
	height: 30px;
    background-image: url( 'img/stones.png');
	background-position:-60px 0px;
}

.gmk_intersection[data-color="black"], .gmk_stone[data-color="black"] {
	background-position:0px 0px;
}

.gmk_intersection[data-color="white"], .gmk_stone[data-color="white"] {
	background-position:-30px 0px
}

These styles rely on an PNG image (with transparent background) of both the white and black stones, and positions the background appropriately to show only the part of the background image matching the appropriate stone (or the transparent space if there is no stone). Here is what the image looks like:

The red circle is used to highlight intersections where you can drop a stone when the player's cursor hovers over them (we also change the cursor to a hand). To do this:

• we define in the css file the 'clickable' css class

.clickable {
	cursor: pointer;
}
.clickable:hover { background-position: -90px 0px; }

• in .js, when we enter the 'playerTurn' state, we add the 'clickable' style to the intersections where there is no stone

        onEnteringState: function( stateName, args )
        {
            console.log( 'Entering state: '+stateName );
            
            switch( stateName )
            {
            
                case 'playerTurn':
                    if( this.isCurrentPlayerActive() )
                    {
                        document.querySelectorAll('.gmk_intersection[data-color="empty"]').forEach(elem => elem.classList.add('clickable'));
                    }            
            }
        },

Finally, make sure to modify the default colors for players to white and black

         $default_colors = array( "000000", "ffffff", );

The basic game turn is implemented: you can now drop some stones!

Cleanup your styles

Remove temporary css visualisation helpers : looks good!

Add some counters in the player panels

Edit .js->setup() to setup the player panels with this extra information

            // Setting up player boards
            for( var player_id in gamedatas.players )
            {
                var player = gamedatas.players[player_id];
                         
                // Setting up players boards if needed
                document.getElementById('player_board_'+player_id).insertAdjacentHTML('beforeend', `
                <div class="cp_board">
                    <div id="stoneicon_p${player.player_id}" class="gmk_stoneicon" data-color="${player.color}"></div><span id="stonecount_p${player.player_id}">0</span>
                </div>
                `);
            }

Add some styles in your .css

.gmk_stoneicon {
	width: 14px;
	height: 14px;
	display: inline-block;
    position: relative;
    background-repeat: no-repeat;
    background-image: url( 'img/stone_icons.png');
    background-position: -28px 0px;
    margin-top: 4px;
    margin-right: 3px;
}

.gmk_stoneicon[data-color="000000"] {
	background-position:0px 0px
}

.gmk_stoneicon[data-color="ffffff"] {
	background-position:-14px 0px
}

.cp_board {
	clear: both;
}

In your Game.php, create a function to return your game counters

    /*
        getGameCounters:
        
        Gather all relevant counters about current game situation (visible by the current player).
    */
    function getGameCounters($player_id) {
    	$sql = "
    		SELECT
    			concat('stonecount_p', cast(p.player_id as char)) counter_name,
    			case when p.player_color = 'white' then 180 - count(id) else 181 - count(id) end counter_value
    		FROM (select player_id, case when player_color = 'ffffff' then 'white' else 'black' end player_color FROM player) p
    		LEFT JOIN intersection i on i.stone_color = p.player_color
    		GROUP BY p.player_color, p.player_id
    	";
    	if ($player_id != null) {
    		// Player private counters: concatenate extra SQL request with UNION using the $player_id parameter
    	}
    
    	return $this->getNonEmptyCollectionFromDB( $sql );
    }

Return your game counters in your Game.php->getAllDatas()

        // Counters
        $result['counters'] = $this->getGameCounters($current_player_id);

And pass them in any notification that needs to update them e.g. Include 'counters' in the "stonePlayed" notification code

        // Notify all players
        $this->notifyAllPlayers( "stonePlayed", clienttranslate( '${player_name} dropped a stone ${coordinates}' ), array(
            'player_id' => $player_id,
            'player_name' => $this->getActivePlayerName(),
            'coord_x' => $coord_x,
            'coord_y' => $coord_y,
            'color' => $color,
            'counters' => $this->getGameCounters($this->getCurrentPlayerId())
        ) );

Finally, in your .js->setup() function call

this.updateCounters(gamedatas.counters);

and in notif_stonePlayed() notification handler function call

this.updateCounters(notif.args.counters);

And define the updateCounters function in your js file (above setup() to avoid error)

updateCounters: function( counters )
{
    for( var counter_container_id in counters )
    {
        var counter_value = counters[counter_container_id]['counter_value'];
        document.getElementById(counters[counter_container_id]['counter_name']).innerText = counter_value;
    }
}

You now have a working counter!

Implement rules and end of game conditions

Implement specific rules for the game. For example in Gomoku, black plays first. So in Game.php->setupNewGame(), at the end of the setup make the black player active:

        // Black plays first
        $sql = "SELECT player_id, player_name FROM player WHERE player_color = '000000' ";
        $black_player = $this->getNonEmptyObjectFromDb( $sql );

        $this->gamestate->changeActivePlayer( $black_player['player_id'] );

Implement rule for computing game progression in Game.php->getGameProgression(). For Gomoku we will use the rate of occupied intersections over the total number of intersections. This will often be wildly inaccurate as the game can end pretty quickly, but it's about the best we can do (the game can drag to a stalemate with all intersections occupied and no winner).

    function getGameProgression()
    {
        // Compute and return the game progression

        // Number of stones laid down on the goban over the total number of intersections * 100
        $sql = "
	    	SELECT round(100 * count(id) / (19*19) ) as value from intersection WHERE stone_color is not null
    	";
    	$counter = $this->getNonEmptyObjectFromDB( $sql );

        return $counter['value'];
    }

Implement end of game detection and update the score according to who is the winner. It is easier to check for a win directly after setting the stone, so:

• declare a global 'end_of_game' variable in Game.php->__construct()

       $this->initGameStateLabels( array(
                 "end_of_game" => 10,
       ) );

• init that global variable to 0 in Game.php->setupNewGame()

       $this->setGameStateInitialValue( 'end_of_game', 0 );

• add the appropriate code in Game.php before proceeding to the next state, using a checkForWin() function implemented separately for clarity. If the game has been won, we set the score, send a score update notification to the client side, and set the 'end_of_game' global variable to 1 as a flag signaling that the game has ended.

        // Check if end of game has been met
        if ($this->checkForWin( $coord_x, $coord_y, $color )) {

            // Set active player score to 1 (he is the winner)
            $sql = "UPDATE player SET player_score = 1 WHERE player_id = $player_id";
            $this->DbQuery($sql);

            // Notify final score
            $this->notifyAllPlayers( "finalScore",
    					clienttranslate( '${player_name} wins the game!' ),
    					array(
    							"player_name" => $this->getActivePlayerName(),
    							"player_id" => $player_id,
    							"score_delta" => 1,
    					)
   			);

            // Set global variable flag to pass on the information that the game has ended
            $this->setGameStateValue('end_of_game', 1);

            // End of game message
            $this->notifyAllPlayers( "message",
    				clienttranslate('Thanks for playing!'),
    				array(
    				)
    		);

        }

Add the checkForWin() function into the Utility Functions area in your Game.php.

    function checkForWin( $coord_x, $coord_y, $color )
    {
        // Get intersections in the same row
        $sql = "SELECT
                    id, coord_x, coord_y, stone_color
                FROM
                    intersection
                WHERE 
                    coord_y = $coord_y
                ORDER BY
                    coord_x
               ";
        $intersections = $this->getCollectionFromDb( $sql );

        if ( $this->checkFiveInARow( $intersections, $coord_x, $coord_y, $color ) ) {
            return true;
        }

        // Get intersections in the same column
        $sql = "SELECT
                    id, coord_x, coord_y, stone_color
                FROM
                    intersection
                WHERE 
                    coord_x = $coord_x
                ORDER BY
                    coord_y
               ";
        $intersections = $this->getCollectionFromDb( $sql );

        if ( $this->checkFiveInARow( $intersections, $coord_x, $coord_y, $color ) ) {
            return true;
        }

        // Get intersections in the same top to bottom diagonal
        $sql = "SELECT
                    id, coord_x, coord_y, stone_color
                FROM
                    intersection
                WHERE 
                    ( cast(coord_x as signed ) - cast( coord_y as signed) ) = $coord_x - $coord_y
                ORDER BY
                    coord_x
               ";
        $intersections = $this->getCollectionFromDb( $sql );

        if ($this->checkFiveInARow( $intersections, $coord_x, $coord_y, $color)) return true;

        // Get intersections in the same bottom to top diagonal
        $sql = "SELECT
                    id, coord_x, coord_y, stone_color
                FROM
                    intersection
                WHERE 
                    coord_x + coord_y = $coord_x + $coord_y
                ORDER BY
                    coord_x
               ";
        $intersections = $this->getCollectionFromDb( $sql );

        if ($this->checkFiveInARow( $intersections, $coord_x, $coord_y, $color)) return true;

        return false;
    }

Then add the checkFiveInARow() function into the Utility Functions area in your Game.php.

    function checkFiveInARow( $intersections, $coord_x, $coord_y, $color )
    {
        $j=0;
        foreach ($intersections as $intersection)
        {
            if ($intersection['stone_color'] == $color) {
                $j=$j+1;
            }
        }
        if ($j>=5) return true;

        return false;
    }

• Then in the gomoku->stCheckEndOfGame() function which is called when your state machine goes to the 'checkEndOfGame' state, check for this variable and for other possible 'end of game' conditions (draw).

    function stCheckEndOfGame()
    {
        $this->trace( "stCheckEndOfGame" );

        $transition = "notEndedYet";

        // If there is no more free intersections, the game ends
        $sql = "SELECT id, coord_x, coord_y, stone_color FROM intersection WHERE stone_color is null";
        $free = $this->getCollectionFromDb( $sql );

        if (count($free) == 0) {
            $transition = "gameEnded";
        }        

        // If the 'end of game' flag has been set, end the game
        if ($this->getGameStateValue('end_of_game') == 1) {
            $transition = "gameEnded";
        }
                
        $this->gamestate->nextState( $transition );
    }

• Catch the score notification on the client side in .js->setupNotifications(). It is advised to set up a small delay after that so that end of game popup doesn't show too quickly.

                dojo.subscribe( 'finalScore', this, "notif_finalScore" );
	        this.notifqueue.setSynchronous( 'finalScore', 1500 );

• Implement the function declared to handle the notification.

            notif_finalScore: function( notif )
	    {
	        console.log( '**** Notification : finalScore' );
	        console.log( notif );
	      
                // Update score
                this.scoreCtrl[ notif.args.player_id ].incValue( notif.args.score_delta );
	    },

Test everything thoroughly... you are done!