Millennia ago, a device known as The System was created by an ancient alien race. This device was told to contain ultimate knowledge and wisdom, however, only those aware of its secrets could hope to choose the right approach towards it. Should The System be accessed the wrong way, it would transfer itself into an instrument of immense destruction. Human beings took that risk, and were punished: The System activated its defense mechanism, and used its weapons against the human race. Years have passed, and the humans managed to learn the techniques contained within The System. Now only one task was left: to shut down The System itself...

Zanac A.I. is a 2D vertically scrolling shooter. You are flying the fighter AFX-6502 Zanac, a space ship built by 256 Riot Fleet as man's last hope against total annihilation. On board are special weapons to help you blast your way through twelve screens of enemy creatures and destroy The System's home base. Zanac is divided into 12 "areas", which look like planets. The various locations range from deserts to jungles and from oceans to industrial zones.

The game has many different types of enemies. Its artificial intelligence program can intensify the action based upon your level of skill. The better you are, the more powerful The System is. The behavior of the randomly approaching enemies is based on factors such as the position of your ship on the screen, the place you last died, etc. The shooting speed of regular enemies and bosses varies as well. At the end of each area (level) you'll have to fight the area boss. Area bosses are mainly presented large, screen-filling bunker bases consisting of gun turrets and a "core". You also have limited time for fighting against the area boss, running out of time could lead to failure in entering the next stage, and penalty of more and more enemies attacking.