Part 22: Secret Level 05
Featured music - "Monkey Hip Dysplasia" and "Nun" from Vitriol and "Far" from Trebuchet by George Hrab.
This is certainly the trickiest secret level in the game. It's a lot like the first secret level, but with many more doors and control panels. The best thing to do in this mine is to place markers in doors that you must open by traveling through a certain point or by opening with a control panel.
I wish I knew more about which panels open which doors. There are so many and that I've left so many markers inside of doors that I can't even tell which door a panel opens.