The combination of three game play mechanics is topped up with fierce invading aliens and three different types of tough and heroic troopers. The player is given the command of a brigade poised to take what ever the horde of aliens can throw at them. The goal is simple: Defend the bunker for as long as possible. Boom Brigade features three classes: minigun troopers, shotgun troopers and bazooka troopers. Any combination of classes can be used when assembling the squad. The player starts with one trooper and receives reinforcements as the alien attack continues. Weapon upgrades and bunker repairs can be bought with the loot the player collects from the aliens.