I very strongly recommend that anyone who hasn't played Part One do that first. Link below.
Soundtrack available here.
These are the lost levels I've going on about. Four levels made out of all the combinations of hazards and enemies I thought were too difficult for Part One, as well as a couple of bosses I cooked up, and two bits of Algernon's back story which can be accessed at any time via the bottom two doors in the level hub.
I can't say enough how much I appreciate all the feedback I've received, it's been an enormous help. Thank you everyone.