let gravity = 9.0;

let mass = 2.0;

​

function setup() {

  createCanvas(720, 400);

  fill(255, 126);

  // Inputs: x, y, mass, gravity

  s1 = new Parts(0.0, width / 2, mass, gravity);

  s2 = new Parts(0.0, width / 2, mass, gravity);

}

​

function draw() {

  background(0);

  s1.update(mouseX, mouseY);

  s1.display(mouseX, mouseY);

  s2.update(s1.x, s1.y);

  s2.display(s1.x, s1.y);

}

​

function Parts(xpos, ypos, m, g) {

  this.x = xpos; // The x- and y-coordinates

  this.y = ypos;

  this.vx = 0; // The x- and y-axis velocities

  this.vy = 0;

  this.mass = m;

  this.gravity = g;

  this.radius = 30;

  this.stiffness = 0.1;

  this.damping = 0.7;

​

  this.update = function (targetX, targetY) {

    let forceX = (targetX - this.x) * this.stiffness;

    let ax = forceX / this.mass;

    this.vx = this.damping * (this.vx + ax);

    this.x += this.vx;

    let forceY = (targetY - this.y) * this.stiffness;

    forceY += this.gravity;

    let ay = forceY / this.mass;

    this.vy = this.damping * (this.vy + ay);

    this.y += this.vy;

    this.y = this.y + this.radius > height ? height - this.radius : this.y;

  };

​

  this.display = function (nx, ny) {

    noStroke();

    ellipse(this.x, this.y, this.radius * 2, this.radius * 2);

    stroke(255);

    line(this.x, this.y, nx, ny);

  };

}

​