text: class Stone{
          constructor(x, y, r) {
            let options = {
              restitution: 0.8
            };
        
            this.body = Bodies.circle(x, y, r, options);
            this.r = r;
            this.color = color;
            World.add(world, this.body);
          }
        
          display() {
            let pos = this.body.position;
            push();
            translate(pos.x, pos.y);
            strokeWeight(1);
            fill("white");
            ellipseMode(RADIUS);
            ellipse(0, 0, this.r, this.r);
            noStroke();
            pop();
          }
        
  }