TypeScript class with no dependencies to handle Sokoban games in less than 10 lines of code. HTML5 example powered by Phaser

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One of the principles of coding is to build scripts as much reusable as you can. This is why I already built a pure JavaScript Sokoban class with no dependencies to handle Sokoban games.

This time I am showing you an even simpler TypeScript class to handle Sokoban games. It’s so simple you will be able to build a Sokoban game in less than 10 lines of code, and you’ll only need to manage user input and visual output.

Look at the game:

Move the character with ARROW keys.

If you want to solve the level, here is the walkthrough:

RDDLRUULDLDDLDDRURRUUULLDDLDRUUURRDLULDDLDDRUUURRDDLRUULLDLDDRU

Now, let’s have a look at the source code, made of one HTML file and 5 TypeScript files:

index.html

The webpage which hosts the game

<!DOCTYPE html>
<html>
	<head>
        <style type = "text/css">
            * {
                padding: 0;
                margin: 0;
            }
            body{
                background: #000;
            }
            canvas {
                touch-action: none;
                -ms-touch-action: none;
            }
        </style>
        <script src = "main.js"></script>
    </head>
	<body>
        <div id = "thegame"></div>
	</body>
</html>

gameOptions.ts

All configurable game options are stored in this file. This time we only need one options, but you’ll never know

// CONFIGURABLE GAME OPTIONS

export const GameOptions = {

    // size of each tile, in pixels
    tileSize : 40
}

main.ts

This is where the game is instanced, with all Phaser related options

// MAIN GAME FILE

// modules to import
import Phaser from 'phaser';
import { PreloadAssets } from './preloadAssets';
import { PlayGame} from './playGame';

// object to initialize the Scale Manager
const scaleObject : Phaser.Types.Core.ScaleConfig = {
    mode : Phaser.Scale.FIT,
    autoCenter : Phaser.Scale.CENTER_BOTH,
    parent : 'thegame',
    width : 320,
    height : 320
}

// game configuration object
const configObject : Phaser.Types.Core.GameConfig = {
    type : Phaser.AUTO,
    backgroundColor : 0x262626,
    scale : scaleObject,
    scene : [PreloadAssets, PlayGame],
    pixelArt : true
}

// the game itself
new Phaser.Game(configObject);

preloadAssets.ts

Here we preload all assets to be used in the game. Only one image this time, but again, you’ll never know.

// CLASS TO PRELOAD ASSETS

import { GameOptions } from "./gameOptions";

// this class extends Scene class
export class PreloadAssets extends Phaser.Scene {

    // constructor    
    constructor() {
        super({
            key : 'PreloadAssets'
        });
    }

    // method to be execute during class preloading
    preload(): void {

        this.load.spritesheet("tiles", "assets/tiles.png", {
            frameWidth : GameOptions.tileSize,
            frameHeight : GameOptions.tileSize
        });
	}

    // method to be called once the instance has been created
	create(): void {

        // call PlayGame class
        this.scene.start('PlayGame');
	}
}

playGame.ts

This is the mail game file, when I handle user input and visual output.

I highlighted the Sokoban related lines, so you can see how it’s simple to build your own game starting from my TypeScript class:

// THE GAME ITSELF

// modules to import
import { GameOptions } from './gameOptions';
import { Sokoban } from './sokoban';

// this class extends Scene class
export class PlayGame extends Phaser.Scene {

    sokobanGame : Sokoban;

    arrowKeys : Phaser.Types.Input.Keyboard.CursorKeys;

    isPlayerMoving : boolean;

    // constructor
    constructor() {
        super({
            key: 'PlayGame'
        });
    }

    // method to be called once the class has been created
    create() : void {

        // player is not moving
        this.isPlayerMoving = false;

        // Sokoban level in standard text notation
        const levelString : string = '########\n#####@.#\n####.$$#\n#### $ #\n### .# #\n###    #\n###  ###\n########';
 
        // create a new Sokoban instance
        this.sokobanGame = new Sokoban();
 
        // build the Sokoban level
        this.sokobanGame.buildLevelFromString(levelString);

        // iterate through all level actors
        this.sokobanGame.actors.map((actor) => {

            // add the sprite
            let sprite : Phaser.GameObjects.Sprite = this.add.sprite(GameOptions.tileSize * actor.column, GameOptions.tileSize * actor.row, 'tiles', actor.type);
            
            // set sprite registration point
            sprite.setOrigin(0);
            actor.data = sprite;
        });

        // initialize arrow keys
        this.arrowKeys = this.input.keyboard.createCursorKeys();
    }    
    
    update() : void {

        // is the player moving?
        if (this.isPlayerMoving) {

            // are all arrow keys unpressed?
            if (!this.arrowKeys.up.isDown && !this.arrowKeys.right.isDown && !this.arrowKeys.down.isDown && !this.arrowKeys.left.isDown) {
                
                // player is no longer moving
                this.isPlayerMoving = false;
            }
        }

        // player is not moving
        else {

            // we store player move in this variable
            let playerMove : (number | null) = null;

            // is "up" arrow key pressed?
            if (this.arrowKeys.up.isDown) {

                // playerMove is up
                playerMove = this.sokobanGame.up;
            }

            // same concept for right direction
            if (this.arrowKeys.right.isDown) {
                playerMove = this.sokobanGame.right;
            }

            // same concept for down direction
            if (this.arrowKeys.down.isDown) {
                playerMove = this.sokobanGame.down;
            }

            // same concept for left direction
            if (this.arrowKeys.left.isDown) {
                playerMove = this.sokobanGame.left;
            }

            // does player move have a value?
            if (playerMove != null) {

                // player is moving
                this.isPlayerMoving = true;

                // loop through all movements
                this.sokobanGame.move(playerMove).map((move) => {

                    // set new position of the actor
                    move.actor.data.setPosition(GameOptions.tileSize * move.to.column, GameOptions.tileSize * move.to.row);
                    
                    // set new frame of the actor
                    move.actor.data.setFrame(this.sokobanGame.getValueAt(move.to.row, move.to.column));

                    if (this.sokobanGame.solved) {
                        this.cameras.main.shake(500);
                    }
                });
            }
        }
    }  
}

sokoban.ts

And finally the TypeScript class you can use in your projects, no matter the framework you are about to use.

It’s fully commented so I am sure you will find it quite clear:

// tile types: 0: floor, 1: wall, 2: goal, 3: crate, 4: player, 5 (3+2): crate on goal, 6 (4+2): player on goal
enum tileType {
    FLOOR,
    WALL,
    GOAL,
    CRATE,
    PLAYER       
}

// player direction: 0: up, 1: right, 2: down, 3: left 
enum playerDirection {
    UP,
    RIGHT,
    DOWN,
    LEFT
}

// SOKOBAN CLASS    
export class Sokoban {

    // movement information mapping for up, right, down and left diretion
    private movementInfo : SokobanCoordinate[] = [
        new SokobanCoordinate(-1, 0),
        new SokobanCoordinate(0, 1),
        new SokobanCoordinate(1, 0),
        new SokobanCoordinate(0, -1)
    ];
     
    // possible string items according to sokoban level notation standard
    private stringItems : string = ' #.$@*+';
   
    // the player
    private player : SokobanActor;

    // the crates
    private crates : SokobanActor [];

    // the tiles
    private tiles : SokobanActor[]; 

    // the level
    private level : number [][];

    // constructor
    constructor() {

        // initialize all arrays
        this.crates = [];
        this.level = [];
        this.crates = [];
        this.tiles = [];
    }

    // method to build a level form a string
    // argument: the string, which we assume to be correct
    buildLevelFromString(levelString: string) : void {

        // split the string in rows
        let rows : string[] = levelString.split("\n");

        // iterate through all rows
        for (let i : number = 0; i < rows.length; i ++) {

            // set level i-th row
            this.level[i] = [];

            // iterate through all columns (string's characters)
            for (let j : number = 0; j < rows[i].length; j ++) {

                // get tile value according to its position in stringItems string
                let value = this.stringItems.indexOf(rows[i].charAt(j));

                // set level value
                this.level[i][j] = value;

                // create the actors to be placed in this tile
                this.createActors(i, j, value);
            }
        }
    }

    // method to create actors
    // arguments: level row, level column and level value
    private createActors(row : number, column : number, value : tileType) : void {

        // a simple switch to handle different values
        // it could be optimized but I prefer to show you how to do it case by case
        switch (value) {

            // floor, goal and wall are simple elements, as there is only one actor: the floor, the wall or the goal
            case tileType.FLOOR :
            case tileType.WALL :
            case tileType.GOAL :

                // add the actor to tiles array
                this.tiles.push(new SokobanActor(row, column, value));
                break;

            // anything with a crate enters this block of code, now we have to split crate and floor type
            case tileType.FLOOR + tileType.CRATE :
            case tileType.GOAL + tileType.CRATE :

                // add the actor below the crate in tiles array
                this.tiles.push(new SokobanActor(row, column, value - tileType.CRATE));

                // add the crate actor in crates array
                this.crates.push(new SokobanActor(row, column, tileType.CRATE));
                break;

            // same concept is applied to the player
            case tileType.FLOOR + tileType.PLAYER :
            case tileType.GOAL + tileType.PLAYER :
                this.tiles.push(new SokobanActor(row, column, value - tileType.PLAYER));
                this.player = new SokobanActor(row, column, tileType.PLAYER);
                break;
        }
    }

    // getter to get "up" direction value
    get up() : number {
        return playerDirection.UP;
    }

    // getter to get "down" direction value
    get down() : number {
        return playerDirection.DOWN;
    }

    // getter to get "left" direction value
    get left() : number {
        return playerDirection.LEFT;   
    }

    // getter to get "right" direction value
    get right() : number {
        return playerDirection.RIGHT;   
    }

    // getter to get all Sokoban actors
    get actors() : SokobanActor[] {

        // for a matter of z-indexing, first I return all floor tiles, then all crates
        let actorsArray : SokobanActor[] = this.tiles.concat(this.crates);

        // finally, the player is added
        actorsArray.push(this.player);
        return actorsArray;    
    }

    // method to get a tile value
    // arguments: the row and the column
    getValueAt(row : number, column: number) : number {
        return this.level[row][column];
    }

    // method to check if the level is solved
    get solved() : boolean {

        // we don't want to find crates
        return this.level.findIndex(row => row.includes(tileType.CRATE)) == -1;    
    }

    // method to move the player, if possible, and return an array of movements
    // argument: the direction
    move(direction: playerDirection) : SokobanMovement[] {

        // array to store movements
        let movements : SokobanMovement[] = [];

        // check if it's a legal move
        if (this.canMove(direction)) {

            // determine player destination
            let playerDestination : SokobanCoordinate = new SokobanCoordinate(this.player.row + this.movementInfo[direction].row, this.player.column + this.movementInfo[direction].column);
            
            // loop through all crates
            this.crates.forEach ((crate : SokobanActor) => {

                // if there is a crate on destination tile...
                if (crate.row == playerDestination.row && crate.column == playerDestination.column) {

                    // determine crate destination
                    let crateDestination : SokobanCoordinate = new SokobanCoordinate(this.player.row + 2 * this.movementInfo[direction].row, this.player.column + 2* this.movementInfo[direction].column);

                    // move the crate
                    movements.push(this.moveActor(crate, new SokobanCoordinate(crate.row, crate.column), crateDestination));
                }
            });

            // move the player
            movements.push(this.moveActor(this.player, new SokobanCoordinate(this.player.row, this.player.column), playerDestination));
        }
        
        // return movements array
        return movements;
    }

    // method to check if a tile is walkable
    // arguments: tile row and column
    private isWalkableAt(row : number, column : number) : boolean {

        // tile is walkable if it's a floor or a goal
        return this.getValueAt(row, column) == tileType.FLOOR || this.getValueAt(row, column) == tileType.GOAL;
    }

    // method to check if there is a crate on a tile
    // arguments: tile row and column
    private isCrateAt(row : number, column : number) : boolean {

        // there's a crate if the tile is a crate or the tile is a crate over the goal
        return this.getValueAt(row, column) == tileType.CRATE || this.getValueAt(row, column) == tileType.CRATE + tileType.GOAL;
    }

    // method to check if there is a pushable crate on a tile
    // arguments: tile row and column, and movement direction
    private isPushableCrateAt(row : number, column: number, direction : playerDirection) : boolean {
      
        // there's a pushable crate if there is a crate and the destination tile is walkable
        return this.isCrateAt(row, column) && this.isWalkableAt(row + this.movementInfo[direction].row, column + this.movementInfo[direction].column);
    }

    // method to check if the player can move in a given direction
    // argument: the direction
    private canMove(direction : playerDirection) : boolean {

        // determine destination row and column
        let destinationRow : number = this.player.row + this.movementInfo[direction].row;
        let destinationColumn : number = this.player.column + this.movementInfo[direction].column;

        // player can move if destination tile is walkable or is a pushable crate
        return this.isWalkableAt(destinationRow, destinationColumn) || this.isPushableCrateAt(destinationRow, destinationColumn, direction);
    }

    // method to move an actor
    // arguments: the actor, the starting tile and the destination tile
    private moveActor(actor : SokobanActor, from : SokobanCoordinate, to : SokobanCoordinate) : SokobanMovement {
        
        // move the actor
        actor.moveTo(to.row, to.column);

        // adjust level values
        this.level[from.row][from.column] -= actor.type;
        this.level[to.row][to.column] += actor.type;

        // return movement information
        return new SokobanMovement(actor, from, to);
    }    
}

// SOKOBAN ACTOR CLASS
class SokobanActor {

    // actor customizable data
    data : any;

    // actor position
    private position : SokobanCoordinate; 

    // actor tile type
    private _type : tileType;

    // constructor
    // arguments: row, column and tile type
    constructor(row : number, column : number, type: tileType) {
        this.position = new SokobanCoordinate(row, column);
        this._type = type;
    }

    // get type of the actor
    get type() : tileType {
        return this._type;
    }

    // is the actor a crate?
    get isCrate() : boolean {
        return this._type == tileType.CRATE;
    }

    // is the actor the player?
    get isPlayer() : boolean {
        return this._type == tileType.PLAYER;
    }

    // get actor column
    get column() : number {
        return this.position.column;    
    }

    // get actor row
    get row() : number {
        return this.position.row;
    }   

    // method to move the actor
    // arguments: row and column
    moveTo(row : number, column : number) : void {
        this.position.setCoordinate(row, column);
    }
}

// SOKOBAN MOVEMENT CLASS
class SokobanMovement {

    // actor to move
    actor : SokobanActor;

    // current coordinate
    from : SokobanCoordinate;

    // destination coordinate
    to : SokobanCoordinate;

    // constructor
    // arguments: the actor, current coordinate, destination coordinate   
    constructor(actor : SokobanActor, from : SokobanCoordinate, to : SokobanCoordinate) {
        this.actor = actor;
        this.from = new SokobanCoordinate(from.row, from.column);
        this.to = new SokobanCoordinate(to.row, to.column);
    } 
}

// SOKOBAN COORDINATE CLASS
class SokobanCoordinate {

    // row and column, just two values to use as x,y coordinates
    private _row : number;
    private _column : number;

    constructor(row : number, column: number) {
        this._row = row;
        this._column = column;
    }

    // get row
    get row() : number {
        return this._row
    }

    // get column
    get column() : number {
        return this._column;
    }

    // method to set coordinate
    // arguments: row and column
    setCoordinate(row : number, column : number) : void {
        this._row = row;
        this._column = column;
    }
}

Now, I will build a complete Sokoban game with levels starting from this class. Follow me on Twitter to stay up to date, and download the source code to start creating your own Sokoban game.

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