Quite innovative.
I like how the game works and all, how people die and after the wave gets added back. To be honests, this may be one of the best defense games in NG along with Last Stand and Bowmaster (more with the former).
A few things could be some spell power checking... Using ice and fireball is probably all you'll need. Other spells seems useless against such combo. Town upgrades are good... when you are swamped by the demons, and teleporting is unavailable, those guys rips roofs like they were paper. Crossbowmen, are almost just as weak as they come. If they were given either more power or more hp, that would be fine. In any case, good job.