This demo is pretty sick, but I think the dungeon it takes place in does it a disservice. It's only gray and purple. From the GIF I saw on Pinterest (WIP snake boss), and the little secret area in the dark maze which gives you a glimpse of the outside world, the art style can and is a lot more varied in other environments.
Might just be me being a stickler for graphics, but I'd say it would be better were you to make some of those wooden background details in the dungeon brown instead of purple. And add some ivy around the place. Probably wouldn't have gotten very far in the demo had I not seen the aforementioned Pinterest GIF.
--WAIT THIS WAS LAST UPDATED IN 2021 LMAO.
Dude are you making the next Hollow Knight? Well, I'll be keeping an eye out for if this ever does get released, regardless. Godspeed.