: The second door that opens is a series of 3 diamond-shaped rooms, bordered by
: purple lava, and teleporters that do nothing of importance. Problem? No
: switches.
: What am I doing wrong?
Those teleporters actually do something - they take you to another section of similar diamond shaped rooms. Surely you noticed the pattern buffer in one of them. If you look in map mode, you'll see exactly what's happening and that you're physically transported to a different place. On the far wall opposite the PB is the switch you're looking for.