I was looking at post 7drl 3D roguelikes for inspiration and this one takes the cake. The combat is satisfying, and the game loops are all fun. The fundamentals here are strong enough to flesh out into a sellable game, but of course it would need a lot more content. In particular, I would like to see some meta-progression, like in FTL, Binding of Isaac, or Enter the Gungeon. I also think that having books give you a choice of 2 or 3 upgrades would make gameplay more strategic. The physics puzzle room is very clever, and I'd love to see more puzzles like this: It breaks up the combat, and it gives a purpose to the under-used slide mechanic.