Simple Galaga Clone

I've been working a lot with html5 and javascript recently, and created a little galaga clone.  Here it is:
(use arrow keys to move and 'X' to shoot)
NEW VERSION!
Changelog:

• Fixed flickering bugs
• Re-added explosions and shrapnel.
• Added new boss on level 100.
• Added a special surprise after level 100(Trust me, It's worth it.)

Known Bugs:

• Boss fights crash the game. Simply refresh the browser to fix this until the next boss. I apologize for the inconvenience, I'm working on it.