// 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 particles = [];

let springs = [];

let spacing = 50;

let k = 0.1;

​

let gravity;

​

function setup() {

  createCanvas(windowWidth, windowHeight);

  for (let i = 0; i < 10; i++) {

    particles[i] = new Particle(width / 2, i * spacing);

    if (i !== 0) {

      let a = particles[i];

      let b = particles[i - 1];

      let spring = new Spring(k, spacing, a, b);

      springs.push(spring);

    }

  }

​

  particles[0].locked = true;

​

  gravity = createVector(0, 0.1);

}

​

function draw() {

  background(112, 50, 126);

​

  for (let s of springs) {

    s.update();

    //s.show();

  }

​

  noFill();

  stroke(252, 238, 33);

  strokeWeight(8);

  beginShape();

  let head = particles[0];

  curveVertex(head.position.x, head.position.y);

  for (let p of particles) {

    p.applyForce(gravity);

    p.update();

    curveVertex(p.position.x, p.position.y);

    //p.show();

  }

  let tail = particles[particles.length - 1];

  curveVertex(tail.position.x, tail.position.y);

  endShape();

​

  fill(45, 197, 244);

  ellipse(tail.position.x, tail.position.y, 64);

​

  if (mouseIsPressed) {

    tail.position.set(mouseX, mouseY);

    tail.velocity.set(0, 0);

  }

}

​