Kingdom Rush is very good game. It's tower defense game with friendly free-to-play model, when you don't need spend any money. There are many towers, heroes (3 heroes are free), enemies and missions. Graphics is nice, sounds is ok too. You can play missions again to gain more stars (rating) or play harder difficulty. There is catchy upgrade system units and towers or you can spend crystals (credits) for support items. I am very interested in sequel and prequel.