This game looks nice and has so much strategic/tactical potential: Dropping towers on the enemy, shifting towers around to assist/complement each other, matching towers to enemy clases, etc.
However, one hardly has to use any of that to beat the game. It is a nice concept, but way too easy. You can win the game by constantly casting the much overpowered spells. Also, the number/strength of the enemy waves is sometimes pretty low, even in higher levels. The bosses don't do anything, too.
This could be a a good RTS game, but as it is, it is not challenging and rather repetitive.