class Pendulum {

  constructor(x, y,a,b, len) {

    //radius

    this.r = 12;

    //length of constrain

    this.len = len;

    this.anchor = Bodies.circle(x, y, this.r, { isStatic: true });

    this.bob = Bodies.circle(a, b, this.r, { restitution: 1.1 });

​

    let options = {

      bodyA: this.anchor,

      bodyB: this.bob,

      length: this.len,

    };

    this.arm = Matter.Constraint.create(options);

    //add constituents to world

    Composite.add(engine.world, this.anchor);

    Composite.add(engine.world, this.bob);

    Composite.add(engine.world, this.arm);

  }

​

  // Drawing the box

  show() {

    fill(127);

    stroke(0);

    strokeWeight(2);

​

    line(

      this.anchor.position.x,

      this.anchor.position.y,

      this.bob.position.x,

      this.bob.position.y

    );

​

    // push();

    // translate(this.anchor.position.x, this.anchor.position.y);

    // rotate(this.anchor.angle);

    // circle(0, 0, this.r * 2);

    // line(0, 0, this.r, 0);

    // pop();

​

    push();

    translate(this.bob.position.x, this.bob.position.y);

    rotate(this.bob.angle);

    circle(0, 0, this.r * 2);

    pop();

  }

}

​