Plot
Suffocating yourself in any way for long enough will eventually cause you to noclip into the backrooms, where you have to travel through all 5 levels to escape:
Level 0 ---------------------- The backrooms we all know and love
Level 1 ---------------------- The Habitable Zone
Level 2 ---------------------- Pipe Dreams
The Poolrooms -------------- The Poolrooms O.o
The Infinite Grass Field ----- This one's different