This was short, but sweet! The mechanics are solid, the visuals are kinda retro which is neat, and the sound effects were good.
I do agree every other comment here though about explaining the controls. Specifically regarding the checkpoints, which I really appreciate you adding, but it's never explained what they are and how to use them. I also don't recall it ever being said how to reload the revolver, I just followed my FPS instincts and pressed R.
I like the semi-stealth system with the lantern, though I think I did get spotted despite not having the lantern out. I'm guessing it just reduces enemy vision distance by half or something. It would be cool if it could've been expanded upon to have the player be illuminated by the environment so you'd have to quickly move through some areas when an enemy isn't around.
The combat was solid, if basic. The hit feedback on the zombies felt obvious which is good, though I felt like the damage might have been random sometimes? The first zombies I was able to kill in 2 hits, then I shot another zombie from a little further away and it took 4 shots, and yet another fairly close up took 3. Does the damage output scale based on distance?
Aside from that, I liked how the pressure plate traps gave you a second or two before activating with a clear audio cue. Allowed some room for error, but only if you pay attention and move quickly.
Regarding the length, I personally prefer this be only a few minutes with unique scenarios in each level, rather than be 40 minutes long but become tedious.
Overall this was nice, good work!