Post your high score if you beat the game.
Not actually sure, because it's drawn in transparent white and the first two characters are on top of a health powerup. I think it's 454535. (Edit: oh, wait, it's changed the window title: 474535). Obviously it's possible to get an infinite score if you really care about it.
Solid concept, although not really enough depth for 8 levels. If you have the spare bytes, some indication in the UI of the number of keys you're currently carrying would be nice. Also I didn't realise until about level 5 that you can kill the spawn points: that makes it a lot easier.