I like the idea!
I would like to give a few suggestions: I didn't find a way of rebooting the level, so I need to refresh the page and try again all the levels I've already passed. Also, I think it would be interesting to have some sprite showing the goal (like a finish flag or something). On the level menu, I believe it would look better if the blocked levels had different colors (gray, for example).
Congrats for the game!