Learn the musical scales while saving the world!
A large number of ships are approaching earth. Some of them are friendly, but others are trying to destroy the world! Using the musical scales as code, protect friendly ships that belong in the scale and destroy the other ships that do not. The more you know your scales, the better you can defend earth. Hitting a friendly ship will damage your space turret which is repaired at the start of every wave. However, any enemy ships that make it to earth will explode and permanently damage the planet. The scales change every wave to throw the enemy off, but they will start sending advanced ships that will be harder to hit. Good luck, you are earth’s only hope against the Full Scale Attack!