Hey, I believe that it is a really cool concept! I love the art style. For now it's hard to rate the gameplay highly because as you said it yourself in the description, it is not exactly finished. I am really interested in how the game will look like if you decide to continue development. Few tips:
For the first few minutes I wasn't really sure what to do at all. I broke the block next to the axe stand and tried to leave the area. It would be nice to indicate that we are supposed to dig down :)
I think that adding an outline to the tile that you can break would help a lot. While we are at it, it would also be nice to be able to break tiles diagonally from the player - this way we could make make-shift staircases for getting back to the surface.
I already saw that you have many ideas regarding this project from your itch.io page and they all seem great! I followed you and I can't wait to se where this project goes