GasLight is a highly customizable iTunes visualizer. Nothing groundbreaking – it’s essentially yet another frequency spectrum analyzer. You can use a whole lot of graphical tricks.

It’s written in a mutant hybrid of Cocoa and Carbon, and uses OpenGL for the graphics work. It currently uses fragment shaders for the nifty glow effects – which are only supported on the Radeon 9600-9800 and the GeforceFX. It will still run on other cards though – it’s just that the glow effects won’t be quite as refined…

Extensive use of PBuffers means that OS X Panther/Tiger is required – don’t even bother trying to run it on anything before that.

And no, this won’t run on the Windows version. I use a bunch of Apple specific OpenGL extensions, and the windowing code and configuration options are heavily tied to Mac code. I don’t have any plans to port this in the near future.