Zanac (ザナック) is an shoot 'em up game originally released for the Famicom Disk System in 1986 by Compile and later ported to the NES and MSX home computer. The game was rereleased the next year for the MSX2 as Zanac EX and was later made available to the PlayStation in Japan as part of Zanac X Zanac.
The technology for faster-than-light travel was developed by humankind in only a short time. One of the expeditionary forces sent to investigate the stars near our galaxy believed they had found a relic of an intelligent extraterrestrial culture, and with this, the "Icon" (Holy Statue) was discovered.
The Icon appeared to be intended to test the people who contacted it. If those people looked for the proper procedure, they would be able to open it in a nondestructive way and would receive beneficial knowledge in return. However, if they instead were impatient and used force to open it, it would reward them with destruction. The expeditionary force, each one of them suspecting that something was hidden inside, were impatient to make the discovery and turned their spacecraft's on-board weapons on the Icon. From the ruins of the destroyed Icon emerged a message which triggered the awakening of a huge battle "System", lying in wait in space.
However, it seemed as if there existed another chance to make up for humankind's failed test by the Icon. Another expeditionary team, unaware of the danger to Earth, encountered another Icon separate from the one that was destroyed, and were able to open it correctly. The Icon transmitted this success to the System, requesting it to halt its attack. But the System, having remained waiting an extreme length of time that its designers could not have predicted, had degraded to the point where it would no longer stop until its target was annihilated and thus had become a simple instrument of mass destruction. Because of this, the order to stop was disregarded and the attack on Earth has begun.
In spite of the overwhelming difference in attack power, humanity went out to meet the approaching machines. Fortunately, one of the Icons was still operating normally, and from information obtained from it, a proposal was made to save Earth. The System was a tactical machine, designed to battle against countless enemies. There was little hope of an all-out attack succeeding, but if a very small-scale attack with very strong attack power was used, a hidden thrust with a needle, so to speak, the System would not be able to cope with it successfully. Then, by striking at the core, the System would be defeated.
Thus, the AFX battle machine (commonly known as ZANAC), the hidden trump card against the System, was constructed and departed for the battle to save humanity.
Zanac is a vertically scrolling shooter where players must control the Zanac fighter through twelve levels in order to defeat the System. The ship's primary weapon is a forward firing pea shooter, which is powered up by collecting yellow orbs released from floating blue boxes. Players can also equip a secondary weapon, which comes with limited ammo and is represented by a number, with a total of eight different weapons available. By picking up the corresponding numbered icon, the ship's secondary weapon is changed to that particular weapon, while picking up an icon from a already equipped weapon will both restore it's ammo and power it up.
The main feature of Zanac is it's Automatic Level of Difficulty Control (ALC), a form of dynamic difficulty where the game's challenge constantly shifts according to the player's skill level. By constantly firing the ship's weapons the enemies become more aggresive, while constantly destroying them makes the game send in tougher enemy patterns. At key points in the stages the player has to destroy a ground fortress within a time limit. Succesfully destrying them will grant a score bonus and reduce the enemy's strength, while failure to destroy them will strengthen the enemies.