Just recently got into this.For some reason it didn't appeal to me a while back when I tried but I gave it another go.

Anyway it's basically a Multiplayer Co-op Tower defence game if you don't know.It's quite a fun game reminds me of Battlezone 2 with everyone able to work independently but at the same time co-operatively(everyone lays there own tower defences).Unlike most TD games your not soley dependendant on your traps/towers as you have can go out with your avatar and kill the enemy in fact you can outkill your towers depending on how you level up your avatar.You also get different classes and each class has there own tower defences types.You can actually interact with other players towers either repairing them or upgrading them.I recommend the PC version over the handhelds as it has a closed server mode so no cheaters.