Zanac

ZANAC A.I. is a 2D shoot them up game. You are flying fighter model ZANAC, a 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, featuring many different types of enemies.

Zanac's unique artificial intelligence program can intensify the action based upon your level of skill. The better you are, the more powerful "The System". Examples of the A.I. (but not limited to) in this game: the enemies are generally coming randomly with their behavior based on factors like the position your ship in the screen, the place you last died; the shoot speed of the enemies and bosses do also vary.

At the end of each area (level) you'll have to fight the area boss. Area bosses are mainly based around huge, screen-filling bunker bases consisting of gun turrets and a "core". You have limited time for fighting against the area boss - a time out could mean failure in entering the next stage, and with the time running, more and more enemies were attacking as penalty.