This was pretty good! It really captured that Backrooms feeling.
When I went through the white gate on Level 5, the game just closed. I'm not sure if that's supposed to be the ending or if it crashed. A message or some kind of ending screen would probably make that clearer.
I got lost quite a few times. 😄
On the mountain level, it might be worth preventing the player from leaving the playable area. I think I spent about five minutes running in one direction, expecting to eventually reach the edge of the map, but it just kept going.