Understanding HTML5 sprite animation with Phaser

Talking about Jet Set Willy game, Game development, HTML5, Javascript and Phaser.

What can make a game to be a great game, apart from game design and gameplay is the animation of the sprites. If you played computer games in stone age, you will surely remember the first Prince of Persia. It was a fair platform game, but the animation of the captive prince was awesome in 1989 – and it still rocks anyway – and made the game fly to worldwide success. While I can’t teach you how to create woderful sprite animations – my graphic skills are around “3 years old baby” level – I can show you how to manage animations in your HTML5 games with Phaser. In today’s example we have the ero taken from Jet Set Willy game, and you can make it “walk” – actually it does not move yet – by pressing Z or X keys. Try it by yourself:
Pressing X it will walk right, pressing Z it will walk left, and doing any other thing than pressing X or Z will make it stop. Remember to mantain the focus in the small game window. All starts from this sprite sheet, which I zoomed in a bit: Then, here is the fully commented source code to turn this sprite sheet into a walk animation: 
<pre class="wp-block-syntaxhighlighter-code">var game;

window.onload = function() {
	game = new Phaser.Game(480, 60, Phaser.AUTO, "");
     game.state.add("PlayGame", playGame);
     game.state.start("PlayGame");
}

var playGame = function(game){};
playGame.prototype = {
     preload: function(){
          // the hero is a spritesheet with all animation frames
          game.load.spritesheet("hero", "hero.png", 20, 32);
     },
     create: function(){
          // the hero is initally placed like a normal sprite
          this.hero = game.add.sprite(game.width / 2, game.height / 2, "hero");
          // flag to determine if the hero is supposed to move right
          this.hero.goingRight = false;
          // flag to determine if the hero is supposed to move left
          this.hero.goingLeft = false;
          // default idle frame, with the hero facing right
          this.hero.idleFrame = 0;
          // this is how we set an animation, we give it a name and an array with the frames.
          var walkRightAnimation = this.hero.animations.add("walkRight", [0, 1, 2, 3]);
          var walkLeftAnimation = this.hero.animations.add("walkLeft", [4, 5, 6, 7]);
          // these are just listeners for X and Z keys
          this.rightKeyPressed = game.input.keyboard.addKey(Phaser.Keyboard.X);
          this.leftKeyPressed = game.input.keyboard.addKey(Phaser.Keyboard.Z);          
          // setting goingRight to true if X is pressed
          this.rightKeyPressed.onDown.add(function(){
               this.hero.goingRight = true;     
          }, this);
          // setting goingRight to false if X is released
          this.rightKeyPressed.onUp.add(function(){
               this.hero.goingRight = false;     
          }, this);  
          // setting goingLeft to true if Y is pressed
          this.leftKeyPressed.onDown.add(function(){
               this.hero.goingLeft = true;     
          }, this);
          // setting goingLeft to false if Y is released
          this.leftKeyPressed.onUp.add(function(){
               this.hero.goingLeft = false;     
          }, this);
     },
     update: function(){
          // if we are going left and not right (we don't want two keys to be pressed at the same time)
          if(this.hero.goingRight && !this.hero.goingLeft){
               this.hero.animations.play("walkRight", 10, true); // <- Look!! This is how I play "walkRight" animation at 10fps with looping
               // idle frame with hero facing right
               this.hero.idleFrame = 0;     
          }
          else{
               // if we are going right and not left
               if(!this.hero.goingRight && this.hero.goingLeft){
                    this.hero.animations.play("walkLeft", 10, true); // <- Look!! This is how I play "walkLeft" animation at 10fps with looping 
                    // idle frame with hero facing left
                    this.hero.idleFrame = 4;      
               }
               else{
                    // show idle frame
                    this.hero.frame = this.hero.idleFrame;         
               }
          }
     }            
}</pre>
In a few lines I animated a sprite, now it’s your turn to draw amazing animations and create the next Prince of Persia (or even better, in my opinion, Jet Set Willy) made with Phaser! Meanwhile, download the source code.