var w, h, ctx, tot = 41;
        function reset() {
            w = window.innerWidth;
            h = window.innerHeight;
            c.width = w;
            c.height = h;
            ctx = c.getContext('2d');
          tot=(Math.max(w, h)/40)|0
        }
        var colors=['#ff0000', '#ff7f00', '#ffff00', '#00ff00', '#0000ff', '#4b0082', '#8b00ff'];
        reset();
        function anim() {
            window.requestAnimationFrame(anim);

            ctx.fillStyle = 'rgba(0, 0, 0, 0.02)';
            ctx.fillRect(0, 0, w, h);

            for (var i = 0; i < tot; ++i) {

                var x = (Math.random() * w) | 0;
                var y = (Math.random() * h) | 0;
                var r = (Math.random() * i) | 0 + 3;

                ctx.fillStyle = colors[i % colors.length];
                ctx.beginPath();
                ctx.arc(x, y, r, 0, Math.PI * 2);
                ctx.fill();
                ctx.closePath();

                ctx.fillStyle = 'rgba(0, 0, 0, 0.6)';

                ctx.beginPath();
                ctx.arc(x, y, r - 2, 0, Math.PI * 2);
                ctx.fill();
                ctx.closePath();
            }
        }
        anim();
        window.onresize = reset;