Well done, the music was well fitting and the theme interpretation is great. Maybe in a next version after the jam you could add some post-processing to improve the graphics. But overall I enjoyed it. Well done.
Me too, I did my game without an engine and adding camerashake and postprocessing might be a bit complicated. My suggestion would be (it isn't real postprocessing but improves the graphics) to add some kind of shadows in the UI for example, or to make the screen darker on the edges to make it feel more creepy.
Overall still a great game, nice that you made that with HTML and JavaScript! Well done