Attack Force was the third arcade-inspired video game that Big Five Software released for the TRS-80. This time the inspiration was the arcade game Targ.
In Attack Force, the player steers a ship through a grid patrolled by eight alien Ramships. The object of the game is to shoot the Ramships and avoid colliding with them.
As in the other Big Five games, the twist comes with the addition of the Flagship alien. In Attack Force, each wave starts off with one or more Flagships patrolling along the right hand edge of the screen, outside of the game grid. The Flagships will occasionally fire a laser bolt which will convert Ramships into Flagships. The Flagships can also turn one of the Ramships into a duplicate of the player's ship. Shooting this duplicate causes the player's ship to be destroyed, calling for careful shooting once a duplicate ship appears.
Once the player has destroyed all of the Ramships, the Flagships will move into the game grid and start shooting laser bolts at the player's ship. The player completes the wave by destroying the Flagships. An increasing number of bonus points are awarded after each completed wave, and extra ships are awarded at each 10,000 points.