Just some experiments with <canvas> and making little stars appear. Processing.js would make this trivial, probably, but I wanted to dabble a bit more.
Mousing over the canvas will litter it with stars. You can also click to put a new one in a spot. Click on "Start Animation" to start them moving (new stars are still added as you mouse over during animation), or "Stop Animation" to, well, stop the animation.
Stars will appear with random color and rotation and scale. Rotation and scale change with each tick of the animation, but color does not. There's also a random rate of fall for each star.