context.save();
        context.fillStyle = BACKGROUND_COLOR;
        context.fillRect(0, 0, screenWidth, screenHeight);
        context.fillStyle = grad;
        context.fillRect(0, 0, screenWidth, screenHeight);
        context.restore();

        for (i = 0, len = gravities.length; i < len; i++) {
            g = gravities[i];
            if (g.dragging) g.drag(mouse);
            g.render(context);
            if (g.destroyed) {
                gravities.splice(i, 1);
                len--;
                i--;
            }
        }

        bufferCtx.save();
        bufferCtx.globalCompositeOperation = 'destination-out';
        bufferCtx.globalAlpha = 0.35;
        bufferCtx.fillRect(0, 0, screenWidth, screenHeight);
        bufferCtx.restore();


        // for (i = 0, len = particles.length; i < len; i++) {
        //     particles[i].render(bufferCtx);
        // }
        len = particles.length;
        bufferCtx.save();
        bufferCtx.fillStyle = bufferCtx.strokeStyle = '#fff';
        bufferCtx.lineCap = bufferCtx.lineJoin = 'round';
        bufferCtx.lineWidth = PARTICLE_RADIUS * 2;
        bufferCtx.beginPath();
        for (i = 0; i < len; i++) {
            p = particles[i];
            p.update();
            bufferCtx.moveTo(p.x, p.y);
            bufferCtx.lineTo(p._latest.x, p._latest.y);
        }
        bufferCtx.stroke();
        bufferCtx.beginPath();
        for (i = 0; i < len; i++) {
            p = particles[i];
            bufferCtx.moveTo(p.x, p.y);
            bufferCtx.arc(p.x, p.y, p.radius, 0, Math.PI * 2, false);
        }
        bufferCtx.fill();
        bufferCtx.restore();


        context.drawImage(bufferCvs, 0, 0);

        requestAnimationFrame(loop);
    };
    loop();

})();