One of the best in the jam. I knew right from the lovely title screen that it was going to be good. I get the point but I think I might consider speeding up the player a little bit at the very start. It's my feeling that an HTML5 game needs to grab you in the first few seconds of gameplay, and honestly the first few seconds of gameplay here felt like a letdown (after the exciting title screen and music). It improved VASTLY after a few upgrades, but I just feel it took a little bit too long to get there. It should never feel like a chore to play a game, and it did for the slightest bit there at the start.
That's really the only criticism I can think of. Great music & sound. Lovely graphics. Smooth gameplay (aside from my critique), interesting level layouts. This is a winner. Great stuff, kudos all around.