Just as i said, i played your game. Its ok, but it has a lot it could have done better. For the main thing, it seems to always at some point just send you into a grey void where you just die with no obvious reason for it. This is a frustrating experience when it doesnt have to be. The enemies, whenever you faced them, felt very generic in their movement, but it also feels like the game wasnt suited for how they move either. They have the type of movement where the player would have a machine gun and blast down large hordes of them, i think anyway, theres probably more than one way to do this, i just dont think this specific way worked all that well. They also didnt give any feedback when they took damage, not even a little flash or flicker, and since the bullets dont get destroyed upon collision it seems like its not hurting them. Though i could see that being intentional. Speaking of, i think you nailed the nightmare vibe, you dont really know whats going on, and randomly teleporting around makes it feel like you are disoriented but not at the same time. Its definitely got a vibe to it. Though i do think it also could have benefited with some more detailed artwork, doesnt have to be much, but grey squares will always make a game look rather generic.
But yeah, good start, keep it up, and i hope my feedback helps!