Not bad. I liked that it was short and you tried to keep things moving by not dragging out the length of the hallways or filling it with too many jump scares as well as by adding some interactive gameplay like the little code puzzle even though it wasn't difficult.
I think the game's strength is changes in the environment, things appearing/disappearing when we face a certain direction, triggered events like the text on the wall, etc. So maybe focus more on the timing and polish of those kinds of things and keep it about the atmosphere. I'd cut out the monster all together since it kind of downgrades the game to something more hokey and doesn't fit, but that's just me. Keep developing and improving and good luck with your next game!