Really promising idea, unfortunately the realization still needs some work.
The concept of a dungeon building game is one I find always appealing, and here it is made even more appealing by the cool art style, but unfortunately I couldn’t progress further than level 4 because heroes got stuck on each other: seeing as they don’t really need to collide with anything you could remove the collisions altogheter! Another thing I’ll say is in a possible post-jam version the room upgrades will need some way to visually distinguish them, be it a number overlayed on top or completely different sprites.
I would also allow heroes to move together to gradually increase difficulty. As I said, as a proof of concept this game has much potential, if you keep working on it and give the player a little more action you can make it a really fun game!