Their over-abundant research with the energy leads to the construction of a weather control machine called ONI, developed entirely for the purpose of taking over the world.

One or two players can take their pick of three helicopters, each with their own firing pattern and battle oncoming waves of enemies through 7 different stages, each with a boss at the end.

Each boss has a different form at the beginning, such as a train, boat, airplane, or submarine, but after the players have inflicted enough damage, it turns into a giant robot.

The first 4 stages, either Alpine Armored Train, Submergence City, Sea of Cloud, or Marine Base, are chosen in random order.

• the Hokum, which is yellow and is the best helicopter, considering it has guided missiles, bullets that deal high damage, and a Special Attack that is 99 rounds and includes small planes that fire at the enemy and follow you around.