Sprinkles Spiral

index.html

<canvas id="canvas"></canvas>

script.js

/*
  Johan Karlsson, 2022
  https://twitter.com/DonKarlssonSan
  MIT License, see Details View
*/

class Bouncer{
  constructor(x, y, dir, useRandomRotation) {
    this.x = x;
    this.y = y;
    this.dir = dir;
    this.speed = 1;
    if(useRandomRotation) {
      this.angle = Math.random() * Math.PI * 2;
      const rotDirection = Math.random() > 0.5 ? 1 : -1;
      this.rotSpeed = (Math.random() * 0.1 + 0.01) * rotDirection;
    } else {  
      this.angle = 0;
      this.rotSpeed = 0.09;
    }
  }
  
  move(delta) {
    this.x += Math.cos(this.dir) * delta * this.speed;
    this.y += Math.sin(this.dir) * delta * this.speed;
    this.angle += this.rotSpeed * delta;
    this.speed += 0.01 * delta;
  }
  
  draw() {
    const s = Math.min(w, h) * 0.02;
    ctx.save();
    ctx.translate(this.x, this.y);
    ctx.rotate(this.angle);
    ctx.fillRect(-s/2, -s/20, s, s/10);
    ctx.restore();    
  }
}

let canvas;
let ctx;
let w, h;
let bouncers;
let then;
let useRandomRotation;

function setup() {
  canvas = document.querySelector("#canvas");
  ctx = canvas.getContext("2d");
  resize();
  window.addEventListener("resize", () => {
    resize();
    reset();
  });
  canvas.addEventListener("click", reset);
  reset();
}

function resize() {
  w = canvas.width = window.innerWidth;
  h = canvas.height = window.innerHeight;
}

function reset() {
  bouncers = [];
  useRandomRotation = Math.random() > 0.5;
}

function addBouncer(angle, r) {
  const x1 = Math.cos(angle) * r + w / 2;
  const y1 = Math.sin(angle) * r + h / 2;
  const b1 = new Bouncer(x1, y1, angle, useRandomRotation);
  bouncers.push(b1);
}

function clear() {
  ctx.fillStyle = "white";
  ctx.fillRect(0, 0, w, h);
}

function draw(now) {
  requestAnimationFrame(draw);
  clear();
  ctx.fillStyle = "black";
  const r = Math.min(w, h) * 0.1;
  const angle = now * 0.005;

  addBouncer(angle, r);
  addBouncer(-angle, r);

  const delta = (now - then) * 0.1;
  bouncers.forEach(b => {
    b.move(delta);
    b.draw();
  });
  bouncers = bouncers.filter(b => b.x >= 0 && b.x <= w && b.y >= 0 && b.y <= h);
  
  then = now;
}

setup();
draw(performance.now());

sprinkles-spiral.markdown

Sprinkles Spiral

A Pen by Johan Karlsson on CodePen.

License.

style.css

body, html {
  margin: 0;
  overflow: hidden;
}

canvas {
  display: block;
  cursor: pointer;
}