The bad: Green sludge. I hate it. I'd rather you kill me in real life than make me wade through the antifun goop again. In the majority of cases the run dies with the goop so you may as well just kill the player outright. Tiny mushrooms seem to have a slightly too small hitbox. The mana regen, its not great but I get why it exists. However, combined with procgen AND nonlinear levels it becomes a nightmare. Having to slowly jog back through a room because you picked a deadend in a 4 way intersection which you had no way to practice or know about beforehand is infuriating. As you get better at navigating the rooms the game becomes less about solid platforming and more about guessing the correct path. Very few room tiles makes the macro-level navigating confusing and repetitive, though I imagine this will be fixed naturally over time as more tiles get made.
The good: Visually its quite nice. Hopefully more tilesets will be added in the future to break up the visual repetitiveness, but what you have now is good. Skeleton animations are good, let me finger gun even if there's nothing to interact with. The seal system is great, I can definitely see myself spending a lot of time messing with different builds ASSUMING route optimization ever becomes a thing, because right now due to the risk of time and monetary loss due to bad door RNG it feels too mandatory to play it as safe as possible with the timer. I did enjoy the general level loop of finding the static heart which tells you which of the dynamic faces you need to hunt for before backtracking to the start. When the game works it works well.