Short but fun! I liked the pixel art, and while I didn't find the art alone very scary (though that may just be because I find shadow monsters more cool than anything), the sound effects did an amazing job of setting the tone. The puzzles did lean a bit into trial-and-error for me, but the checkpoints are frequent enough that dying to one of the monsters isn't really a problem, at least on the first ending route. A simple tip for the first route: once the monsters start shimmering in the dark, they can be gotten rid of.
The trial-and-error was a bit more frustrating on the second ending route, since there's only one screen and thus a single checkpoint at the start, where you have to wait a few seconds for the main character to wake up each time you restart. I feel like if that animation was skipped when you respawn, the trial-and-error would have bothered me a lot less, though.
One last thing; press F during the credits for a nice surprise!