Thanks guys!
Kyatric
Strictly canvas. WebGL works OK with this, but it won't let me zoom in without blurring the graphics (point sampling doesn't seem to work) and causing some other problems.
Yeah I use Chrome with GPU Accelerated Canvas 2D enabled, and FRAPS for recording. It actually runs at a (mostly) smooth 60fps but I think youtube caps it at 30fps.
About the Bulloom (flower enemy) part.. I just kept doing the spin attack too early! You can jump on that enemy instead, but it's kind of risky as it spits those projectiles straight upwards. It might be a good idea to shrink those gaps a bit though.
I don't think there's anything I can do about the music looping. It just doesn't loop instantly in C2, and the pause is pretty noticeable. I tried pre-loading the music but it didn't make any difference. The intro is a lot 'softer' than the ending too, but that's only half the problem!