Good concept of the game. But the further you go the more expensive an upgrade will be and they want you to watch ads to get further . For example, in like lvl 6 or so, an upgrade that you need to get is 7k to do any damage to a tower. But your income is only 420 gold a minute. If you get far enough you'll get a chest with 10k and a key to unlock heros. If you do the math you won't make it. So you'll have to watch an ad to get the upgrade, if it isn't enough, time runs out. An add has to be w.