Vertical Force is a Virtual Boy video game released in 1995. Developed by Hudson Soft and published by Nintendo (Japan) and Hudson Soft (United States), Vertical Force is a shoot 'em up title developed exclusively for the ill-fated system.
Taken directly from the Vertical Force manual:
"A battle that will either wipe humanity or machines from the universe has begun! The year is 210 SE (Space Era). Humankind has prospered beyond the wildest imagination of the earliest space explorers. Waves of human colonists have advanced to thousands of planets all over the universe. Each colony built is provided with a caretaker computer and equipped with Android Industrial (AI) Drones to control the planet and mine resources. The materials collected are sent back to Earth.
Now, something has gone terribly wrong and the caretaker computer of Odin, (planet #0326) has spontaneously reprogrammed itself. Instead of serving humans and sending minerals to Earth, it seems its new mission is to slaughter humans and make minerals of Earth.
The corrupted caretaker, calling itself "Mittgard," has declared war on all humanity. His mechanical army of "AI Drones" is headed toward Earth,and he has equipped them with a ray that will render the strategic computers and weapons of the United Earth Army inoperative. As a result, wherever the army has tried to intercept the AI Drones has suffered total defeat. As luck would have it, a xeno-archealogy team working on Ragnarok (planet#1562) has just made a most fortuitous find. Among the ruins of an alien civilization, a battle machine has been unearthed. Because of its alien design and construction, this battle machine is not affected by the Mittgard rays. The most fortunate stroke is that it is equipped with a device that allows it to reprogram some AI Drones and use them against Mittgard's forces. After taking possession of the Ragnarok battle machine, The United Earth Army has called on its number one flying ace, YOU, to rid the universe of the menace posed by Mittgard."