No music, average graphics, lack of a hint feature and other annoyances make it a 3/5 for me. It seems like you either get the puzzle in like five seconds or it stumps you for several minutes-- there's no in between. Also, I think level 18 was actually quite a bit harder than 19, it was the only one i got stuck on.
It's a challenging game, but I managed to beat it anyway. (and I only had to use the guide for level 10)
All you really need is some good timing, lots of patience and creative thinking and you're set.
To kill the doctor you must use subversion on him when he tries to heal. Subversion will make him do damage to himself instead of healing and he'll kill himself.
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