// The Coding Train / Daniel Shiffman

// https://thecodingtrain.com/CodingChallenges/160-spring-forces.html

// https://youtu.be/Rr-5HiXquhw

​

// Simple Spring: https://editor.p5js.org/codingtrain/sketches/dcd6-2mWa

// Spring Vector: https://editor.p5js.org/codingtrain/sketches/_A2pm_SSg

// Spring OOP: https://editor.p5js.org/codingtrain/sketches/9BAoEn4Po

// Soft Spring: https://editor.p5js.org/codingtrain/sketches/S5dY7qjxP

​

let bob;

let anchor;

let velocity;

let restLength = 200;

let k = 0.01;

let gravity;

​

function setup() {

  createCanvas(600, 400);

  bob = createVector(350, 0);

  anchor = createVector(300, 0);

  velocity = createVector(0, 0);

  gravity = createVector(0, 0.1);

}

​

function draw() {

  background(112, 50, 126);

  strokeWeight(4);

  stroke(255);

  line(anchor.x, anchor.y, bob.x, bob.y);

  fill(45, 197, 244);

  circle(anchor.x, anchor.y, 32);

  circle(bob.x, bob.y, 64);

​

  if (mouseIsPressed) {

    bob.x = mouseX;

    bob.y = mouseY;

    velocity.set(0, 0);

  }

​

  let force = p5.Vector.sub(bob, anchor);

  let x = force.mag() - restLength;

  force.normalize();

  force.mult(-1 * k * x);

​

  // F = A

  velocity.add(force);

  velocity.add(gravity);

  bob.add(velocity);

  velocity.mult(0.99);

}

​