var w = c.width = window.innerWidth, h = c.height = window.innerHeight, ctx = c.getContext('2d'), cen = {x:w/2, y:h/2}, radiant = 0, particles = [], particleCount = 1, frame = 0, middleCover = ctx.createRadialGradient(cen.x, cen.y, 0, cen.x, cen.y, 20);middleCover.addColorStop(0, 'rgba(0, 0, 0, .1)');middleCover.addColorStop(1, 'rgba(0, 0, 0, 0)');function anim(){ window.requestAnimationFrame(anim); update();}anim();function Particle(){ this.x = cen.x; this.y = cen.y; this.vx = Math.cos(radiant); this.vy = Math.sin(radiant); this.color = 'hsl(rad, 80%, 50%)' .replace('rad', ((radiant/Math.PI)*180)|0);}Particle.prototype.update = function(){ this.x += this.vx; this.y += this.vy; ctx.fillStyle = this.color; ctx.fillRect(this.x, this.y, 2, 2);}function update(){ ctx.fillStyle = 'rgba(0, 0, 0, .04)'; ctx.fillRect(0, 0, w, h); radiant += .1; radiant %= Math.PI*2; ++frame; if(frame > particleCount){ frame = 0; particles.push(new Particle); } for(var i = 0; i < particles.length; ++i){ var par = particles[i]; par.update(); if(par.x > w || par.x < 0 || par.y > h || par.y < 0){ particles.splice(i, 1); --i; } } ctx.fillStyle = middleCover; ctx.beginPath(); ctx.arc(cen.x, cen.y, 20, 0, Math.PI*2); ctx.fill();}document.addEventListener('click', function(){ for(var i = 0; i < 10; ++i) update();})for(var i = 0; i < 100; ++i) update();

See the Pen Spiral of rainbowy particles by towc (@MateiGCopot) on CodePen.