Aleph Null is color music. No audio. It's an online, generative, interactive, open source visual work written in JavaScript using the HTML5 canvas tag. No plugin required. There's also a slideshow of screenshots to give you a sense of what it can look like in full flight. Turn the lights off.

It's like hunting the Snark, beauty or butterflies. It takes a little practice. It's like an instrument. Or a game in which the goal is to experience color music and create visuals you like. Unlike most instruments, Aleph Null will play something whether a person is playing or not. But it benefits immensely by a human player. It knoweth not beauty, is but the instrument of thine own incandesence.

Here's an introductory video and an essay on Aleph Null.