So you never saw a creature get generated? If you hit the synthesize button, then I think you ran into a bug! I actually haven't seen this bug before, but I managed to get it just now. Still not sure how, maybe exiting the menu without synthesizing messes it up?
Also, filling out all 4 slots seems to make the creature sometimes fly off of the screen at light speed for some reason, although monsters that only use 1-3 slots mostly seem to work ok. It's weird, I definitely thought I had 4 slot worms working in testing.
The C button opens gates because I knew there were bugs that might make the game unbeatable, it's a special cheat.
I'll have to look these bugs! Thanks for the details!