text: const Engine = Matter.Engine;
  const World = Matter.World;
  const Bodies = Matter.Bodies;
  const Constraint = Matter.Constraint;
  
  var engine, world, backgroundImg,boat;
  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;
    angleMode(DEGREES)
    angle = 15
  
    ground = Bodies.rectangle(0, height - 1, width * 2, 1, { isStatic: true });
    World.add(world, ground);
  
    tower = Bodies.rectangle(160, 350, 160, 310, { isStatic: true });
    World.add(world, tower);
  
    cannon = new Cannon(180, 110, 130, 100, angle);
   
  }
  
  function draw() {
    background(189);
    image(backgroundImg, 0, 0, width, height);
  
    Engine.update(engine);
  
   
    rect(ground.position.x, ground.position.y, width * 2, 1);
    
  
    push();
    imageMode(CENTER);
    image(towerImage,tower.position.x, tower.position.y, 160, 310);
    pop();
  
  
  
    showBoats();
  
    for (var i = 0; i < balls.length; i++) {
      showCannonBalls(balls[i], i);
    }
  
    cannon.display();
  }
  
  function keyPressed() {
    if (keyCode === DOWN_ARROW) {
      var cannonBall = new CannonBall(cannon.x, cannon.y);
      cannonBall.trajectory = [];
      Matter.Body.setAngle(cannonBall.body, cannon.angle);
      balls.push(cannonBall);
    }
  }
  
  function showCannonBalls(ball, index) {
    if (ball) {
      ball.display();
      if (ball.body.position.x>=width || ball.body.position.y>=height){
        ball.remove(index);
      }
    }
  }
  
  function showBoats() {
    if (boats.length > 0) {
      if (
        boats[boats.length - 1] === undefined ||
        boats[boats.length - 1].body.position.x < width - 300
      ) {
        var positions = [-40, -60, -70, -20];
        var position = random(positions);
        var boat = new Boat(width, height - 100, 170, 170, position);
  
        boats.push(boat);
      }
  
      for (var i = 0; i < boats.length; i++) {
        if (boats[i]) {
          Matter.Body.setVelocity(boats[i].body, {
            x: -0.9,
            y: 0
          });
  
          boats[i].display();
        } 
      }
    } else {
      var boat = new Boat(width, height - 60, 170, 170, -60);
      boats.push(boat);
    }
  }
  
  function keyReleased() {
    if (keyCode === DOWN_ARROW) {
      balls[balls.length - 1].shoot();
    }
  }
  function collisionWithBoat(index){
    for (var i=0; i<boats.length; i++){
      if (balls[index]!== undefined && boats[i]!== undefined){
        var collision=Matter.SAT.collides(balls[index].body,boats[i].body);
        if (collision.collided){
          boats[i].remove(i);
  
          Matter.World.remove(world,balls[index].body);
          delete balls[index]
        }
      }
    }
  }