First Good Reverse Tower Defense
Congratulations! This is the first fun, challenging, and well-balanced reverse tower defense game I've ever played. There are just a few balance issues that if fixed could make it even better. First, as fast as I can tell the turtle is never worth building. Because a fully-upgraded raider can take 1200 damage and a fully-upgraded turtle 2000, if you can get the raider through just one round you're better off with the additional point since damage scales 10% per round. Fully-upgraded turtles should have about health, or at least some damage reduction. Second, the cleansers are never worth building. You're always better off using an elemental, then just using the extra mana from it to stun the tower or quake it. Just one elemental can thus protect the whole army, as opposed to at least 2 cleansers. To balance this, cleansers need to have a much larger effective range. If you fixed these problems, you could make the game much more challenging in the later levels and require a more complex strategy than just effective spell use.