Phaser Jump Game

Phaser Jump Game.markdown

Phaser Jump Game

This is a demo that goes along with a forum reply here: http://www.html5gamedevs.com/topic/7369-infinite-world/

Working with a potentially infinite world size can be tricky with Phaser. This method seems to work well though. As you move up, the camera follows the hero. Then, based on how high the hero has reached in comparison to where they started, that offset and height is modified on the world bounds. This allows the world to expand to the exact height that the game requires, all the while using the built in physics system without any trickery for the platforms to work. The player is moving up in world space, while the platforms keep their same coordinates, so it is easier to wrap your head around.

A Pen by Jack Rugile on CodePen.

License.

script.js

var Jumper = function() {};
Jumper.Play = function() {};

Jumper.Play.prototype = {

  preload: function() {
    this.load.image( 'hero', 'https://s3-us-west-2.amazonaws.com/s.cdpn.io/836/dude.png' );
    this.load.image( 'pixel', 'https://s3-us-west-2.amazonaws.com/s.cdpn.io/836/pixel_1.png' );
  },

  create: function() {
    // background color
    this.stage.backgroundColor = '#6bf';

    // scaling
    this.scale.scaleMode = Phaser.ScaleManager.SHOW_ALL;
    this.scale.maxWidth = this.game.width;
    this.scale.maxHeight = this.game.height;
    this.scale.pageAlignHorizontally = true;
    this.scale.pageAlignVertically = true;
    this.scale.setScreenSize( true );

    // physics
    this.physics.startSystem( Phaser.Physics.ARCADE );

    // camera and platform tracking vars
    this.cameraYMin = 99999;
    this.platformYMin = 99999;

    // create platforms
    this.platformsCreate();

    // create hero
    this.heroCreate();

    // cursor controls
    this.cursor = this.input.keyboard.createCursorKeys();
  },

  update: function() {
    // this is where the main magic happens
    // the y offset and the height of the world are adjusted
    // to match the highest point the hero has reached
    this.world.setBounds( 0, -this.hero.yChange, this.world.width, this.game.height + this.hero.yChange );

    // the built in camera follow methods won't work for our needs
    // this is a custom follow style that will not ever move down, it only moves up
    this.cameraYMin = Math.min( this.cameraYMin, this.hero.y - this.game.height + 130 );
    this.camera.y = this.cameraYMin;

    // hero collisions and movement
    this.physics.arcade.collide( this.hero, this.platforms );
    this.heroMove();

    // for each plat form, find out which is the highest
    // if one goes below the camera view, then create a new one at a distance from the highest one
    // these are pooled so they are very performant
    this.platforms.forEachAlive( function( elem ) {
      this.platformYMin = Math.min( this.platformYMin, elem.y );
      if( elem.y > this.camera.y + this.game.height ) {
        elem.kill();
        this.platformsCreateOne( this.rnd.integerInRange( 0, this.world.width - 50 ), this.platformYMin - 100, 50 );
      }
    }, this );
  },

  shutdown: function() {
    // reset everything, or the world will be messed up
    this.world.setBounds( 0, 0, this.game.width, this.game.height );
    this.cursor = null;
    this.hero.destroy();
    this.hero = null;
    this.platforms.destroy();
    this.platforms = null;
  },

  platformsCreate: function() {
    // platform basic setup
    this.platforms = this.add.group();
    this.platforms.enableBody = true;
    this.platforms.createMultiple( 10, 'pixel' );

    // create the base platform, with buffer on either side so that the hero doesn't fall through
    this.platformsCreateOne( -16, this.world.height - 16, this.world.width + 16 );
    // create a batch of platforms that start to move up the level
    for( var i = 0; i < 9; i++ ) {
      this.platformsCreateOne( this.rnd.integerInRange( 0, this.world.width - 50 ), this.world.height - 100 - 100 * i, 50 );
    }
  },

  platformsCreateOne: function( x, y, width ) {
    // this is a helper function since writing all of this out can get verbose elsewhere
    var platform = this.platforms.getFirstDead();
    platform.reset( x, y );
    platform.scale.x = width;
    platform.scale.y = 16;
    platform.body.immovable = true;
    return platform;
  },

  heroCreate: function() {
    // basic hero setup
    this.hero = game.add.sprite( this.world.centerX, this.world.height - 36, 'hero' );
    this.hero.anchor.set( 0.5 );
    
    // track where the hero started and how much the distance has changed from that point
    this.hero.yOrig = this.hero.y;
    this.hero.yChange = 0;

    // hero collision setup
    // disable all collisions except for down
    this.physics.arcade.enable( this.hero );
    this.hero.body.gravity.y = 500;
    this.hero.body.checkCollision.up = false;
    this.hero.body.checkCollision.left = false;
    this.hero.body.checkCollision.right = false;
  },

  heroMove: function() {
    // handle the left and right movement of the hero
    if( this.cursor.left.isDown ) {
      this.hero.body.velocity.x = -200;
    } else if( this.cursor.right.isDown ) {
      this.hero.body.velocity.x = 200;
    } else {
      this.hero.body.velocity.x = 0;
    }

    // handle hero jumping
    if( this.cursor.up.isDown && this.hero.body.touching.down ) {
      this.hero.body.velocity.y = -350;
    } 
    
    // wrap world coordinated so that you can warp from left to right and right to left
    this.world.wrap( this.hero, this.hero.width / 2, false );

    // track the maximum amount that the hero has travelled
    this.hero.yChange = Math.max( this.hero.yChange, Math.abs( this.hero.y - this.hero.yOrig ) );
    
    // if the hero falls below the camera view, gameover
    if( this.hero.y > this.cameraYMin + this.game.height && this.hero.alive ) {
      this.state.start( 'Play' );
    }
  }
}

var game = new Phaser.Game( 300, 500, Phaser.CANVAS, '' );
game.state.add( 'Play', Jumper.Play );
game.state.start( 'Play' );

scripts

<script src="//cdnjs.cloudflare.com/ajax/libs/phaser/2.0.5/phaser.min.js"></script>