The gradients are defined using CSS. I think it might work if someone threw suitable declarations there. I recall IE<9 implement some custom syntax that might work.
I glanced at the code quickly and noticed `addEventListener` without `attachEvent` fallback. So that will fail in at least IE8 and below. Not sure about other things, but I'm guessing you never tried it in IE8?
Nope. Definitely need to add that fallback there. Good point!