Fun game - solid entry, especially considering the time constraints.
Really appreciate the leveling up and the fact you save the process on reloading the game.
three nitpicks:
1. Game slows to crawl when too many monsters are spawned - maybe a HTML 5 problem..
2. Wish there was a way to see your progress - what upgrades you have already selected
3, This one is silly, but the second monsters look much scary than the third ones would switch the order.
Again nice submission, enjoyed it