Simple particles example on the Raspberry Pi using node-openvg-canvas. Original demo code from thecodeplayer.com.

node-openvg-particles.js

// Original Source
// http://thecodeplayer.com/walkthrough/make-a-particle-system-in-html5-canvas
//
// Modified to work with `node-openvg-canvas` on the Raspberry Pi
// - use RequestAnimationFrame instead of setInterval
// - correct the number of arguments in call to `ctx.arc()`
//
// Usage:
// - install Node.JS
//   (refer to Installing Node section here: http://blog.rueedlinger.ch/2013/03/raspberry-pi-and-nodejs-basic-setup/)
//
// - install node-openvg-canvas
//   $ git clone https://github.com/luismreis/node-openvg-canvas.git
//   $ cd node-openvg-canvas
//   $ npm install
//
// - download a copy of this script
// - run it (from inside the `node-openvg-canvas` directory)
//   $ node node-openvg-particles.js

var Canvas = require('./lib/canvas');
var canvas = new Canvas(800, 800);
var ctx    = canvas.getContext('2d');

var numParticles = 10;
var W = canvas.width;
var H = canvas.height;

var particles = [];
for ( var i = 0; i < numParticles; i++ ) {
	particles.push( new Particle() );
}

// Create a function which will help us to create multiple particles
function Particle() {
	// Random position on the canvas
	this.x = Math.random() * W;
	this.y = Math.random() * H;
	
	// Lets add random velocity to each particle
	this.vx = Math.random() * 20 - 10;
	this.vy = Math.random() * 20 - 10;
	
	// Random colors
	var r = Math.random() * 255 >> 0;
	var g = Math.random() * 255 >> 0;
	var b = Math.random() * 255 >> 0;
	this.color = "rgba("+ r +", "+ g +", "+ b +", 0.5)";

	// Random size
	this.radius = Math.random() * 20 + 20;
}

function draw() {
	// Moving this BG paint code insde draw() will help remove the trail
	// of the particle. Lets paint the canvas black
	// But the BG paint shouldn't blend with the previous frame
	ctx.globalCompositeOperation = "source-over";
	
	// Lets reduce the opacity of the BG paint to give the final touch
	ctx.fillStyle = "rgba(0, 0, 0, 0.3)";
	ctx.fillRect(0, 0, W, H);
	
	// Lets blend the particle with the BG
	ctx.globalCompositeOperation = "lighter";
	
	// Lets draw particles from the array now
	for( var t = 0; t < particles.length; t++ ) {
		var p = particles[t];
		
		ctx.beginPath();
	
		// Time for some colors
		var gradient = ctx.createRadialGradient(p.x, p.y, 0, p.x, p.y, p.radius);
		gradient.addColorStop(0,   "white");
		gradient.addColorStop(0.4, "white");
		gradient.addColorStop(0.4,  p.color);
		gradient.addColorStop(1,   "black");
		
		ctx.fillStyle = gradient;

		// NOTE: Was missing the 4th parameter, needed for node-openvg-canvas
		ctx.arc(p.x, p.y, p.radius, 0, Math.PI * 2, false);
		ctx.fill();
		
		// Apply the velocity
		p.x += p.vx;
		p.y += p.vy;
		
		// To prevent the balls from moving out of the canvas
		if ( p.x < -50 )    p.x = W + 50;
		if ( p.y < -50 )    p.y = H + 50;
		if ( p.x > W + 50 ) p.x = -50;
		if ( p.y > H + 50 ) p.y = -50;
	}

	requestAnimationFrame( draw );
}

draw();