Attack Force is based on Targ arcade game released the same year (1980) by Exidy. Bill Hogue and Big Five Software must have worked fast to release their version only a few month later. As Bill Hogue explained in an interview, they naturally got their inspiration from latest games they used to play at the local arcade...

The playing field is made up of a 5 by 7 grid of blocks (a city) while the original arcade version is made of a 9 by 9 grid.

You maneuver your ship on the playfield using the "streets" drawn by the blocks and you must destroy all the ramships which logically try to ram you. While they can't fire back at you, you must avoid them at all cost as any contact will destroy your ship.

One additional feature compared to the original Targ is the flagships! Flagships are waiting at the right side of the screen sometimes flashing ramships to turn them into more aggressive ships. When all ramships are destroyed, flagships enter the playfield. You must then destroy all of them to change level before they disintegrate you with their very deadly laser bolt.

Flaghips are Big Five Software icons. They appear in all their games since the first release (Super Nova). The dreaded flagship has an evil rotating eye and also possess a very deadly laser bolt.

The arcade conversion made by Bill Hogue was very good given the limitation of the TRS-80 hardware. Attack Force plays like Targ (and even more) including the variable speed of your ship.