Multiplayer Tower Defense and Attack. 3 vs 3 battles where you defend your own base while assaulting your opponents. There are many races to choose from each with their own strengths and weaknesses. Some are offensive, defensive, support etc. You have to work together with others to win.
Screenshots of the tutorial and 3 vs 3 games of tower storm.
The tutorial. Fairly basic if you've played tower defense games before but required to explain the concept of attacking and how the more minions you send the more money you make.