My main problem is the 'it's too easy to drop yourself into the hole' thing - that's just made more frustrating by the fact you could have spend a good while clearly one 'screen' and only be waiting for 1 enemy to walk into the trap and boom - there's your "don't take damage" challenge failed (and you're unlikely to want to repeat the level because it's just a BIT too slow and BIT too random).
Remember this is early in the game too - it's fine to put levels which require more 'attention' from the player into the game - but perhaps that in the first 20 mins

I like the concept - I'd like it more if I'd not stared myself blind finding the switches too - remember that people play on different sized screens. I started-off playing this on my laptop (11" screen 1280x800) - I've moved to the desktop now because it's just easier and less migraine-inducing...