The idea is interesting, but by its name, I was expecting it has a mechanic related to the rhythm. I think that if you're going to give the player time before the attack starts, the game should show spawn positions of soldiers so she can plan how to play. Another good thing could be something in the UI that let the player know the path a monster will take. I see the potential for this game as a card game, maybe because of the variety of demons. And having a rhythm mechanic would be great.
Some animations were pretty good.
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