Emanuele Feronato

// the game itself
var game;
// the ship we are controlling
var ship;
// the group with all barriers, which will be used for collision detection
var barrierGroup;
// ship horizontal speed, can be modified to change gameplay
var shipHorizontalSpeed = 400;
// barrier vertical speed, can be modified to change gameplay
var barrierSpeed = 150;
// delay from one barrier and another. This isn't meant to be a time measurement but a pixel measurement.
// that is, a new barrier will be created once the old barrier travelled for 150 pixels
var barrierDelay = 150;
// this is a speed multiplier, useful to make the ship move to the left or to the right. Will assume -1 or +1 values
var speedMult;

// function to be executed once the window finishes to load
window.onload = function() {	
     // creation of a 320x480 game
	game = new Phaser.Game(320, 480, Phaser.AUTO, "");
     // creation of a state called PlayGame, which is the only state
     game.state.add("PlayGame",playGame);
     // starting playGame state
     game.state.start("PlayGame");
}

var playGame = function(game){};

playGame.prototype = {
	// preloading images
     preload: function(){
          // image ship
          game.load.image("ship", "ship.png");
          // horizontal barrier
          game.load.image("barrier", "barrier.png");
          // vertical wall
          game.load.image("verticalbarrier", "verticalbarrier.png");
	},
     // creation of the game
  	create: function(){
          // first we create the group which will contain all obstacles and we add it to the game
          barrierGroup = game.add.group();
          // starting the physics system
          game.physics.startSystem(Phaser.Physics.ARCADE);
          // adding the ship sprite, horizontally centered near the bottom of the canvas
          ship = game.add.sprite(game.width / 2, game.height - 40, "ship");
          // setting the anchor point in the middle of the ship
          ship.anchor.set(0.5);
          // enabling the ship to be part of the physics simulation
          game.physics.enable(ship, Phaser.Physics.ARCADE);
          // don't let the ship rotate
          ship.body.allowRotation = false;
          // when a click/touch is detected, call moveShip function
          game.input.onDown.add(moveShip);
          // when a click touch is released, call stopShip function
          game.input.onUp.add(stopShip);
          // this function will place barriers and is the core of the game
          placeBarriers();           
	},
     update: function(){
          // this will make the ship leave the stage to the left and enter from the right
          if(ship.x < 0){
               ship.x = game.width;
          }
          // this will make the ship leave the stage to the right and enter from the left
          if(ship.x > game.width){
               ship.x = 0;
          }
          // checking for collision between the ship and the barrier group
          game.physics.arcade.collide(ship, barrierGroup, function(){
               // if there's a collision, restart the game
               game.state.start("PlayGame");     
          });
     }
}

// function to move the ship
function moveShip(e){
     // checking if we touched/clicked on the left half of the canvas or on the right half
     if(e.position.x < game.width / 2){
          // left, 
          speedMult = -1;
     }
     else{
          // right
          speedMult = 1;
     }
     // setting ship body horizontal velocity according to shipHorizontalSpeed and speedMult.
     // the ship will move to the left or to the right 
     ship.body.velocity.x = shipHorizontalSpeed * speedMult;
}

// function to stop the ship
function stopShip(){
     // setting ship body horizontal velocity to zero. The ship will stop
     ship.body.velocity.x = 0;     
}

// placeBarriers function will create the whole maze
function placeBarriers(){
     // ther's a 1/10 probability we WON'T place vertical barriers, allowing ths ship to wrap around the canvas
     if(game.rnd.between(0, 9) > 0){
          placeVertical = true;
     }
     else{
          placeVertical = false;
     }
     // posiiton of the hole in the horizontal barrier.
     // it's not an actual hole, just a space between two horizontal barriers
     var position = game.rnd.between(0, 4);
     // creation of a new barrier. Arguments: the barrier itself, the position of the hole, the horizontal registration point (1 = rightmost pixel)
     // and a flag to know if we have to create vertical barriers. This is the LEFT barrier
     var barrier = new Barrier(game, position, 1, placeVertical); 
     // adding the newly created barrier to the game              
     game.add.existing(barrier);
     // adding the newly created barrier to barrierGroup
     barrierGroup.add(barrier);
     // and this is the RIGHT barrier, with registration point to zero (leftmost pixel)
     barrier = new Barrier(game, position + 1, 0, placeVertical); 
     // adding the newly created barrier to the game                    
     game.add.existing(barrier);
     // adding the newly created barrier to barrierGroup
     barrierGroup.add(barrier);
}

// this is the horizontal barrier class
Barrier = function (game, position, anchor, placeVertical) {
     // first we place the sprite. Look at the arguments with x and y positions:
     // x = position * ((game.width - 40 [twice the width of vertical barriers]) / 5 [number of possible holes]) + 20 [width of vertical barrier]
     // y = outside the top of the canvas, -barrierDelay - 40 [twice the width of vertical barriers]
	Phaser.Sprite.call(this, game, position * ((game.width - 40) / 5) + 20, -barrierDelay - 40, "barrier");
	// enabling physics on the barrier
     game.physics.enable(this, Phaser.Physics.ARCADE);
     // setting the anchor point
     this.anchor.set(anchor, 0);
     // here we just set createNew flag to true to left barriers.
     // a barrier with createNew flag will create new horizontal barriers.
     if(anchor == 1){
          this.createNew = true;
     }
     else{
          this.createNew = false;
     }
     // together with horizontal bar, we add a vertical bar, if placeVertical is true
     // then we add it to the game and to barrierGroup
     if(placeVertical){
          var vertical = new Vertical(game, anchor);
          game.add.existing(vertical);
          barrierGroup.add(vertical);
     }
     // setting barrier vertical speed
     this.body.velocity.y = barrierSpeed;
};

Barrier.prototype = Object.create(Phaser.Sprite.prototype);
Barrier.prototype.constructor = Barrier;

// things to do at each frame
Barrier.prototype.update = function() {   
	// if the barrier leaves the stage to the bottom...
     if(this.y > game.height){
          // ... then destroy it
		this.destroy();
	}
     // if the barrier is about to enter the stage and has createNew flag...
     if(this.createNew && this.y >= - 40){
          // remove the flag
          this.createNew = false;
          // place new barriers
          placeBarriers();     
     }
};

// this is the vertical barrier class
// side can be 0 (left) or 1 (right)
Vertical = function (game, side) {
     // adding vertical barrier sprite. The coordinates follow the same concept of the barrier
	Phaser.Sprite.call(this, game, game.width * side, -barrierDelay - 40, "verticalbarrier");
	// enabling physics on the barrier
     game.physics.enable(this, Phaser.Physics.ARCADE);
     // setting the anchor point
     this.anchor.set(side, 0);
     // barrierDelay + 20 [horizontal barrier height]
     this.height = barrierDelay + 20; 
     // setting barrier vertical speed   
     this.body.velocity.y = barrierSpeed; 
};

Vertical.prototype = Object.create(Phaser.Sprite.prototype);
Vertical.prototype.constructor = Barrier;

Vertical.prototype.update = function() {
     // if the barrier leaves the stage to the bottom...
	if(this.y > game.height){
          // ... then destroy it
		this.destroy();
	}
};