Alright, lessee
The cyclical spikes are really impressive, but it would be cool if it was a more elaborate pattern / there were more spikes changing. I don't know how much effort this would be to rig though, havent' peeked at the code yet. Also when I played it I had my volume off, but if there isn't an audio cue when each block "closes" there oughta be one. Overall more spikes placed throughout the narrow area might give a greater sense of danger (not necessarily appearifying ones, just regular spikes). I like the sort of "collapsed" look, with the floor, that'll have to carry through to the next floor up for consistency.
If there's any way to have the left side of the map close in on you (a'la Ballos' Last Throes - that is a specific entity that does those walls) it would make the "oh shit hurry" factor increase and thus further stimulate endorphin release in players, leading to greater satisfaction.