Not bad, overall feels and looks good. I did kind of wish there was something more you could do to determine how battles go, something like being able to peek at rooms and decide if you actually want to do that fight or being able to position your characters before the battle or something.
Also at first I assumed you couldn't go back to rooms you've visited but once I realized you can I assumed that I could just walk past a heart room and come back later to heal.
Edit:Couple of other things, seeing the health of your slimes when deciding on a level reward would be nice due to full heal being an option. Not sure if needing to unequip items from low health slimes to not lose them when they die is a good mechanic and in general changing equipment mid combat to suit the specific enemy slime is fighting feels weird.