Great style, look, and feel to this game. Sound works well to.
Love the concept, and the game mechanics.
I did find it a bit to repetitive. The difficulty didn't ramp up much, it got very samey.
Only once did i get the enemies that spawn the "!" taking out whole rows.
Twice i got the mega spawning demons from bellow.
And first few levels with just the demon spawning dragged on.
Random can be good, but takes away YOUR control on difficulty ramping and development of the overall arch of the game.
Regardless, I did really enjoy playing this game :)! It's really well put together.
Great job, well done. I hope you continue and improve this game after the Jam, as I think it's a great base to build upon to something really great!