I really like this concept! as i was playing it, i found it a bit difficult to balance both tetris and dungeon-crawling. in my opinion the fast paced nature of it lends itself more towards co-op, as you're going throughout the dungeons your friend builds more as fast as he/she can to get you out of situations (also a VS mode would be hella fun).
I feel like adding a seperate gamemode of playing tetris until you die and then making it to the end of whatever dungeon you just built and it gets harder the further you get up the screen would be a great addition to this game.
Sorry for all of the run-on sentences lmao.
im loving it so far! Keep it up!