Guns Up! is free-to-play side-scrolling strategy game that works as a tower defense game but puts you in a role of both attacker and defender, depending on the mission in question. In between missions, the player can build his base, upgrade existing and unlock new units, build structures and place turrets to protect against invading armies, and customize the army. During fights with other players the army gathers experience which can be used for upgrades, in addition to in-app purchases which allow you to do that faster, but for real money.
The battle consists of attacker's army truck approaching enemy base. The truck is filled with certain types of infantry units which can be summoned in exchange for ammunition which is used as a currency for the troops. The defender can do the same, but the defending army exits from the HQ building or the infantry barracks. The attacker's goal is to destroy the enemy HQ. Infantry on both sides will advance toward the enemy and along the way fires automatically. Destroyed enemy troops and structures often leave items which can be picked up and used in battle by the player. The items, among many others, include a rally flag which rallies ones troops, a dummy which forces enemy troops to fire at it instead of your troops, carpet bombing which summons bomber against selected area, a missile strike, tear gas which stuns enemy infantry for a short time, and more.