Its an interesting demo.
Maybe the goal could be to reach higher & higher floors to eventually leave the null; without dying ( say... 10 floors of increasing difficulty ).
I think a creature that fears the light could be neat, running to one of the few lights on a floor to break chase & force it to retreat
Maybe have it a roguelike ( each death is a new run from the bottom ) with permanent perks you could find / take
Or maybe a slow progressing one with checkpoints every floor, with floors taking longer and being harder
( level / floor ) design suggestions are hard because of the many directions this could take for its theme and gameplay loop
