text: const Engine = Matter.Engine;
  const World = Matter.World;
  const Bodies = Matter.Bodies;
  const Body = Matter.Body;
  
  let engine;
  let world;
  var angle=60;
  
  var ground;
  var b1,b2,b3,b4;
  var top_wall;
  var ball,rock;
  
  var btn1;
  var btn2;
  function setup() {
    createCanvas(400,400);
  
    engine = Engine.create();
    world = engine.world;
    
     
    var ground_options ={
      isStatic: true
    };
   
    var ball_options = {
      //write a code to set value of restitution such that:
  //Ball (white circle) bounces more when it hits the bottom.
  restitution: 0.99,
  frictionAir: 0.02
    }
  
    var rock_options = {
     // write a code to set value of restitution such that:
     // Rock (Red Circle) bounces less when it hits the bottom.
     restitution: 0.88,
     frictionAir: 0.02
    }
     
    btn2 = createImg('up.png');
    btn2.position(350,30);
    btn2.size(50,50);
    btn2.mouseClicked(vForce);
    
    ball = Bodies.circle(100,10,20,ball_options);
    World.add(world,ball);
    
    rock = Bodies.circle(250,10,20,rock_options);
    World.add(world,rock);
  
    ground= Bodies.rectangle(200,390,400,20,ground_options);
  
    World.add(world, ground);
   
    
  
    rectMode(CENTER);
    ellipseMode(RADIUS);
  }
  
  
  function draw() 
  {
    background(51);
    Engine.update(engine);
    
  rect(ground.position.x,ground.position.y,400,20);
  ellipse(ball.position.x,ball.position.y,20);
  push();
  fill("brown");
  ellipse(rock.position.x,rock.position.y,20);
  pop();
  }
  
  function vForce()
  {
   //write a code to move ball up when the button is clicked.
   Matter.Body.applyForce(ball,{x:0,y:-0.03},{x:0,y:-0.05});
  }
  