Emanuele Feronato

// the game itself
var game;

// when the window loads...
window.onload = function() {

    // game creation
    game = new Phaser.Game(320, 480, Phaser.CANVAS);

    // adding "Play" state and execute it
    game.state.add("Play", play, true);
}

// "Play" state
var play = function(){}
play.prototype = {

    // when the state preloads
	preload:function(){

        // loading graphic assets
        game.load.image("player", "player.png");
        game.load.image("enemy", "enemy.png");
	},

    // once the state has been created
    create:function(){

        // maximizing the game
        game.scale.scaleMode = Phaser.ScaleManager.SHOW_ALL;
        game.scale.pageAlignHorizontally = true;
        game.scale.pageAlignVertically = true;

        // set the score to zero
        this.score = 0;

        // set top score to local storage saved score, if any, or zero.
        this.topScore = localStorage.getItem("topboomdots") == null ? 0 : localStorage.getItem("topboomdots");

        // adding a text object which will display the score
        this.scoreText = game.add.text(10, 10, "-", {
            font:"bold 16px Arial",
            fill: "#acacac"
		});

        // we'll call this method each time we need to update the score
        this.updateScore();

        // ladies and gentlemen, the player
        this.player = game.add.sprite(game.width / 2, game.height / 5 * 4, "player");

        // set player registration point to its center
        this.player.anchor.setTo(0.5);

        // ladies and gentlemen, the enemy :)
        this.enemy = game.add.sprite(game.width, 0, "enemy");

        // set enemy registration point to its center
        this.enemy.anchor.set(0.5);

        //  method to place the player
        this.placePlayer();

        // method to place the enemy
		this.placeEnemy();
	},

    // function to be executed at each frame
	update:function(){

        // if the player touches the enemy
		if(Phaser.Math.distance(this.player.x, this.player.y, this.enemy.x, this.enemy.y) < this.player.width / 2 + this.enemy.width / 2){

            // stop enemy tween
            this.enemyTween.stop();

            // stop player tween
			this.playerTween.stop();

            // adding one point to the score
			this.score ++;

            // this is a perfect shot: player and enemy are almost aligned on the vertical axis
			if(Math.abs(this.player.x - this.enemy.x) < 10){

                // a bonus score
                this.score += 2;
			}

            // place the enemy again
            this.placeEnemy();

            // place the player again
            this.placePlayer();

            // update score text
            this.updateScore();
		}
	},

    // method to update the score
    updateScore: function(){
		this.scoreText.text = "Score: " + this.score + " - Best: " + this.topScore;
	},

    // method to place the player
    placePlayer: function(){

        // set player horizontal position
        this.player.x = game.width / 2;

        // set player vertical position
        this.player.y = game.height / 5 * 4;

        // player tween to move the player to the bottom of the screen. The higher the score, the faster the tween
        this.playerTween = game.add.tween(this.player).to({
			y: game.height
		}, 10000 - this.score * 10, Phaser.Easing.Linear.None, true);

        // if the tween completes, it's game over and we call die method
        this.playerTween.onComplete.add(this.die, this);

        // waiting for player input to call fire method
        game.input.onDown.add(this.fire, this);
	},

    // game over
	die: function(){

        // update local storage saving the max between current score and top score
		localStorage.setItem("topboomdots", Math.max(this.score, this.topScore));

        // start the game again
        game.state.start("Play");
	},

    // method to place the enemmy
    placeEnemy: function(){

        // set enemy x position
        this.enemy.x = game.width - this.enemy.width / 2;

        // set enemy y position
		this.enemy.y = -this.enemy.width / 2;

        // tween to make the enemy enter on the stage
        var enemyEnterTween = game.add.tween(this.enemy).to({
			y: game.rnd.between(this.enemy.width * 2, game.height / 4 * 3 - this.player.width / 2)
		}, 200, Phaser.Easing.Linear.None, true);

        // once the tween is completed, move the enemy horizontally
        enemyEnterTween.onComplete.add(this.moveEnemy, this);
	},

    // method to move the enemy
    moveEnemy: function(){

        // yoyo tween to move the enemy left and right
        this.enemyTween = game.add.tween(this.enemy).to({
			x: this.enemy.width / 2
		}, 500 + game.rnd.between(0, 2500), Phaser.Easing.Cubic.InOut, true, 0, -1, true);
	},

    // method to fire
    fire: function(){

        // removing input listener
        game.input.onDown.remove(this.fire, this);

        // stop current player tween
        this.playerTween.stop();

        // tween to fire the player to the top of the stage
        this.playerTween = game.add.tween(this.player).to({
			y: -this.player.width
		}, 500, Phaser.Easing.Linear.None, true);

        // if the tween completes, that is the player missed the enemy, then it's game over
        this.playerTween.onComplete.add(this.die, this);
	}
}