text: var trex, trex_running, trex_collided;
  var ground, invisibleGround, groundImage;
  
  function preload() {
    trex_running = loadAnimation("trex1.png", "trex3.png", "trex4.png");
    trex_collided = loadImage("trex_collided.png");
  
    groundImage = loadImage("ground2.png")
  }
  
  function setup() {
    createCanvas(600, 200);
  
    //create a trex sprite
    trex = createSprite(50,160,20,50);
    trex.addAnimation("running", trex_running);
    trex.scale = 0.5;
    
    //create a ground sprite
    ground = createSprite(200,180,400,20);
    ground.addImage("ground",groundImage);
    ground.x = ground.width /2;
    ground.velocityX = -4;
    invisibleGround=createSprite(200,195,400,15);
    invisibleGround.visible=false;
  }
  
  function draw() {
    background(220);
  
    //jump when the space button is pressed
    if (keyDown("space")&&trex.y>150)  { 
      trex.velocityY = -10;
    }
  
    trex.velocityY = trex.velocityY + 0.8
  
    if (ground.x < 0) {
      ground.x = ground.width / 2;
    }
  
    trex.collide(invisibleGround);
    drawSprites();
  }