My land is a variation of the classic tower defense game. In this game two players compete against one another directly. Each player places towers to use to kill off the other persons tanks (uncontrollable npcs which attack the other player). Between the nearest tanks is the limit of your land, and you can only place towers on your land. You can also destroy towers by building on top of them.

Also note that both players see themselves at blue, and the other persons units as yellow.