The overall aesthetic, from sound to art, was really well implemented. It did feel like I was in a nightmare. The upgrade system and format was interesting and made me want to keep running through to make it to the next upgrade room.
Geez that difficulty spike kind of comes out of nowhere though! Being able to shoot on the move would be a great addition. This is a small thing that probably won't affect a lot of people and it's tough to check every scenario for a jam game, but I have a widescreen monitor, so this is what running the game in fullscreen looks like:
I played it in the browser window instead. The nightmare is much more frightening when his back end isn't cut off!
Great work to the entire team. A great approach to a unique boss battle.