One of the most interesting games I've played in awhile. Firstly, this is an FPS. Secondly, it is also a simple strategy game. Thirdly, it is around 800 mb of space.
Basically, you and your "rebels" fight off thousands of enemy imperial soldiers. You must defend your rebel stronghold, while the enemy must kill it off. The main game is in FPS mode. Every player though, depending on how well they do, gains power. With power you can buy traps, guns, bombs, support crates, turrets (both troop and vehicle), among other things. The strategy mode isn't another main mode. Rather every person has it with the press of a button. You can still control your character's movement in this mode. So if you want to plant a trap while running away from gunfire, you can do so.
The maps are set up so that attacks can come from any area, but you also have a good defense and each round is about 30 to 40 minutes of play. You also have the option to repair anything, every character has molotovs, and every character has a knife, pistol, and rifle. Buying weapons with "power" is what customizes your character. Once you buy something in terms of weapons or bombs, you have it forever. When you die, you respawn with those armaments. Spawned turrets have unlimited ammo, and health that you can repair as well.
It is really fun to play this game. It isn't graphically advanced, but it doesn't need to be. A very simple strategy/fps game with a tower defense like mechanic, that doesn't involve any towers.