Lots to like here for an early demo.
The good: I really like the "feel" of the game. The character movement, and combat feels nice, especially when played with a controller. I enjoy the Spelunky-style level generation, and the mixture of enemies and items present. The music is chill and soothing, almost Stardew Valley-esque at times. The UI is looking fantastic, your button / screen designs are smooth.
Possible improvements: The first thing I noticed is I couldn't get Skill 1 to work, but perhaps my controller's LB button is broken and this is the first time I've noticed (ha). I enjoy the item enhancements, but noticed that sometimes they overwrite a previous improvement (at one point I lost my double jump when I acquired another item, which was a bummer). Is there a way to regenerate health? I'm not sure if it is a necessity in the game, but if it is does exist, I didn't figure out how to do it. I also found that when I reached the bottom of each floor the UI began to get in the way - it would be great if the camera panned a little lower so as to not obscure the character / enemies. Lastly, a simple 'pause' menu to exit the game from would be nice.
All in all, great work so far. I look forward to seeing future developments.