Zanac (ザナック) is a shoot 'em up video game developed by Compile and published in Japan by Pony Canyon and in North America by FCI.

[5] The player operates a rapid-fire main cannon, which can be upgraded by collecting power-ups found in blue boxes that periodically descend from the top of the screen.

[10] The distinguishing aspect of Zanac's gameplay is its unique enemy artificial intelligence, called the "Automatic Level of Difficulty Control" or ALC.

[5] The ALC measures the System's aggressiveness and the game's difficulty depending on the actions of the player, such as attack pattern and skill level.

[5] For instance, shooting the main cannon frequently, collecting power-ups, and failing to destroy bosses within the specified time limit increases the ALC, resulting in a greater number of tougher enemies appearing on-screen.

However, actions such as losing lives, starting a new level, or destroying reconnaissance planes reduces the ALC, resulting in fewer on-screen enemies.

The AFX-6502 Zanac, the most advanced starfighter ever produced, is launched on a desperate mission to fight its way to the heart of the System and shut it down.

Compile then re-released the game for the MSX2 computer later that same year as Zanac Ex, which featured improved graphics (with smooth scrolling) and extended music over the original MSX version.

[13] Zanac was then ported and heavily reworked again for release on the Family Computer Disk System in Japan on November 11, 1986,[14] and then in North America for the NES in October 1987.

[22] Brett Alan Weiss of Allgame praised Zanac, calling it an extremely fast-paced shooter in which the player is almost completely surrounded by enemy ships and bullets.

[21] Frank Provo of GameSpot lauded Zanac for its difficulty level, its ability to handle many sprites on the screen without slowdown or other glitches, and its unique AI, which placed this game in a subgenre of its own.