The simplest star field you'll ever find

starfield.html

<title>Starfield</title>
<script>
addEventListener('load', function() {
    var stars = [];
    var ctx = field.getContext('2d');
    var gen = function(z) {
        return {
            x: 0 | (Math.random() * 800 - 400),
            y: 0 | (Math.random() * 600 - 300),
            z: z || (0 | Math.random() * 15)
        };
    }

    for (var i = 0; i < 200; stars.push(gen(i++)));
    setInterval(function() {
        ctx.clearRect(0, 0, 800, 600);
        ctx.font = '20pt Arial';
        for (var star in stars) {
            ctx.fillStyle = '#' + Array(7).join((0 | stars[star].z).toString(16));
            ctx.fillText(
                '*',
                stars[star].x / stars[star].z + 400,
                stars[star].y / stars[star].z + 300
            );
            stars[star].z -= 0.25;
            if (stars[star].z <= 0) {
                stars[star] = gen(15);
            }
        }
    }, 20);
});
</script>
<canvas id="field" width="800" height="600"></canvas>