Needs clarification.
It's a good game, but my biggest peeve was that you didn't know how much damage a unit was doing, and you didn't know how armor value was relative to damage, or how much the training actually increases. It's all guesswork.
Also, the money you get is from defeating units, not beating the enemy, which is lame. I can easily beat an enemy and get just 300 money from a battle or take my time and just kill them off and let the timer run out and earn 1800+. That's not right. It means if you rush ahead to harder levels, you simply can't buy the units/upgrades you need, thus forcing you to restart the game.
I also hate mismatches, where the enemy simply throws waves of superior enemies towards you and you can't fend them off. Like a crushing defeat except you just can't beat them no matter what you do.