Desperately needs a way to reset a level. That way even if things get messed up (as they will at this point in the design process) the tester isn't forced to reload the page. I found myself hopelessly stuck in a wall on the second level, the attack button seemed to do nothing and I'm unsure what the blue number at the top of the screen means. Keep at it and I'm sure these problems can be overcome.
As many previous posters have said, it is far to easy for a single slip to ruin your attempt. This isn't the sort of difficulty that most people find rewarding to overcome. Basing the score on time taken might be a better choice. Minor mistakes would still cost the player, but not necessarily force a reset if the player is quick enough and can see the solution.