Spoiler alert :

Like it has been said early (thanks daivipdaivip), use 2 fire towels to beat level 8.
Use the same technique for level 9 and 10. I passed level 10 with 2 fire and 1 ice.
Also put block on the ground as late as possible, because it widen the castle and make the enemy reach you early.

This game has some potential, but it's still unplayable.

I gave the gave the game a try because of the elephant and balloons picture.
I thought maybe that this may be a cool defense game that I have to figure hidden weaknesses in enemies. I was disappointed.
I'd like to redesign my castle. I'd like a damsel to protect rather a king. I'd like a the king to start dealing more damage and be able to pick out targets better.
The music, and graphics were very good. tweak it out a bit and this game will be more popular.

I was able to make it to Wave 3/5 on State 3: at that point the game becomes unplayable, even with maxed out Damage. The Skill tree has a very basic variety of upgrades which show barely any increase in performance, and respecking made no real difference. Version 1.1 showed little improvement in the balance of difficulty for this game.

It's just not even fun. The enemies have far to many hit points. And like almost all other reviews, the enmies spawn in to higher numbers often with suicide enemies behind others so you can kill them before they get to you.