At first I thought this game had only partially completed combat mechanics, but from reading the other comments here it seems like I got very very unlucky with bugs. I didn't think the revolver even worked because it NEVER fired for me despite being reloaded several times. So I just used the knife for the entire game and to be honest it was a total slog.
The movement was also kinda weird, not the controls themselves those worked pretty ok, but the map itself. It was like half the time I was clipping into level geometry and I was either too far away from objects or right on top of them. This was mitigated a bit by being able to click on things from several tiles away, but that feels more like a bug than intentional design decision.
The combat also felt kinda awkward. There's very little feedback, I mean I can tell I'm dealing damage from the healthbar (which frankly is more feedback than my game's combat has), but it doesn't seem like enemies react. The sound effects could also stand to be beefed up a bit.
The Synty visuals worked well for creating a cosmic horror game, between the sort of haunted house area and the floating ruins level. I especially liked the ending where the house shifts to being corrupted and destroyed.
The overall presentation of the player being a paranormal investigator felt good and very pulp noirish with the opening and closing narration. Just the name Derek Deagle is equal parts cool and ridiculous.
Overall I think there's some good stuff here and I could see players enjoying it. But with that revolver bug it REALLY impacted how tedious this game was to play, so I definitely suggest getting that fixed first. Aside from that you made a game with various mechanics and multiple levels in a short time period, good work!