I passed with 740 kills after some attempts. Using magic tower with freeze is the easyest way to win. Some issues:
1, The use of weapons and the operation of tower upgrades often conflict with each other. Recommended to use double-clicking to open the tower upgrade process.
2, Red demonds is rare, after use up the initial 3000, I didn't know where can collect more.
3, Is Archer tower weakest one? I can't pass the level with archer towers.
4, How to quit to the main menu after win/lost?
5, More levels...