Really cool and unique concept. I feel like there are only a few games in this jam that really went all in on the limitation, and this is one of them.
From the title and screenshots I was expecting it to be a space invaders type of game, but if anything it feels like a reverse space invaders with some tower defense elements. I was pleasantly surprised by how interesting it was. My only gripe is that the attack tile feels too expensive to shoot for how difficult it can be to aim.
The graphical presentation is nice and cohesive, and the sound design also fit well. It all comes together and feels really polished for a jam game.
Nice work!