It's pretty cool and challenging, we liked the difficulty escalation and the different subtle gameplay elements (like picking up the key made you heavier etc). We did get a bit frustrated when we lost in the 3rd stage because we had activated the lever when the green-eyes monster was slightly outside our halo as it seems that despite the light being on at this point, it was still considered "outside the halo" and thus the kill timer ran out during the event sequence.