Max level earthquake and meteorite on a starting castle will destroy it before they can get any people out. Max the +xp skill, farm lvl2 with blind mode and sudden death for 35k+ exp each time.
Magic might be a bit too powerful, since you can kill one enemy team and cripple another before you even leave your first castle.
Multiplayer would be cool.
I beat the game but am ~600 pts short of being able to upgrade everything (due to low scores in the first few levels?) - are you going to make it possible to go back and re-beat levels?
sparta badge is really easy: fully upgraded flamethrower, max walls and as many repairers as possible. rest on gunmen.
just light them on fire as they come, theyll die just before they get to your wall.