text: const Engine = Matter.Engine;
  const World = Matter.World;
  const Bodies = Matter.Bodies;
  const Constraint = Matter.Constraint;
  var engine, world, backgroundImg;
  var canvas, angle, tower, ground, cannon;
  var balls = [];
  var boats = [];
  
  function preload() {
    backgroundImg = loadImage("./assets/background.gif");
    towerImage = loadImage("./assets/tower.png");
  }
  
  function setup() {
    canvas = createCanvas(1200,600);
    engine = Engine.create();
    world = engine.world;
    angle = -PI / 4;
    ground = new Ground(0, height - 1, width * 2, 1);
    tower = new Tower(150, 350, 160, 310);
    cannon = new Cannon(180, 110, 100, 50, angle);
    boat = new Boat(width, height - 100, 200, 200, -100);
  }
  
  function draw() {
    background(189);
    image(backgroundImg, 0, 0, width, height);
  
    Engine.update(engine);
    ground.display();
  
    for (var i = 0; i < balls.length; i++) {
      showCannonBalls(balls[i], i);
    }
    boat.display()
    showBoats();
    cannon.display();
    tower.display();
  }
  
  function keyPressed() {
    if (keyCode === DOWN_ARROW) {
      var cannonBall = new CannonBall(cannon.x, cannon.y);
      balls.push(cannonBall);
    }
  }
  
  //function to show the ball
  function showCannonBalls(ball, index) {
    ball.display();
    if (ball.body.position.x >= width || ball.body.position.y >= height - 50) {
      Matter.World.remove(world, ball.body);
      balls.splice(index, 1);
    }
  }
  
  function showBoats ()
  {
    if (boats.length > 0)
     {
    if ( boats.length < 4 && boats[boats.length - 1].body.position.x < width - 300 )
    {
      var positions = [-130, -100, -120, -80];
      var position = random(positions);
      var boat = new Boat(width,height - 100, 200, 200, position);
       boats.push(boat);
   }
    for (var i = 0; i < boats.length; i++)
     { 
       Matter.Body.setVelocity(boats[i].body,
         {
            x: -0.9, y: 0 }); 
           boats[i].display(); 
         }
   }
  }
  
  function keyReleased() {
    if (keyCode === DOWN_ARROW) { 
      balls[balls.length - 1].shoot();
    }
  }
  