This is a really creative and interesting concept for a game, and it fits the Gameboy aesthetic really well. The gameplay does kind of get a bit repetitive fairly quickly as there isn't that much of a change in difficulty/strategy as you go on. I got to level 7 before letting the enemies kill me, so admittedly there might have been more stuff I missed that came after that.
I do like the idea for the combat though, maybe having enemies that block tiles or do attacks that do something other than just damage would help keep it interesting (Although that'd probably be out of the scope of a game jam lol).