I'm feeling better now and I can tell you what the problem is with
the empty cell room. It's because the hallway at the end of the purple
area leads to the second boss's room, which was the intended 'end' of
the demo. He's horribly unfinished (literally just a head rn) so I just
outright removed the room for the demo. When you touch a room load
trigger that loads a room file that doesn't exist, the game defaults to
reloading the same room you're in but Bugsy's X and Y coordinates are 0.
There's water under every room in the game (defaults to a screen below
the room's lowest point, it just raises or lowers depending on the room
file's internal values) so the game's running as intended in that sense.
There are other rooms this way too, or some that don't have collision
yet and just a basic outline, or some rooms that don't have all the
exits with room load triggers, which allow you to do things like go over
the top of a room and stand inside walls. It's more my fault for not
sealing those unfinished exits and telling the player they're done with
Aside from that the glitches look like relatively simple problems to fix, other than the balloon jellyfish falling (although somehow whenever a tester finds a glitch it ends up taking like 8 hours to fix apiece). The springs suck though, I'm gonna replace them with plants that you jump inside and spit you out, launching you until you hit the ceiling.
I have lots more plans for the higher difficulties. Right now normal enemy placements are set for Normal Mode. I'm not a fan of simply increasing damage and health for enemies. I wanted them to be simple and predictable, but easy to set in any situation, like the monsters in Doom, so I can spam huge numbers of them and still be fair in higher difficulties, like Doom. But on top of that I'm also going to include late game enemies early game and probabaly make harder varients of enemies appear on harder difficulties as well.
My progress is pretty slow because it's a project I manage on my free time when I feel motivated to work on it. I can go a month without touching Fusion, then suddenly work 12-15 hours a day on it over a weekend. Keep your fingers crossed for DD17.