The idea of the game is that you are a tank on enemy grounds trying to prevent the launch of missiles that will basically destroy the world.

The main goal of the game is to a) Get access to the launch code, and b) reach the missile silo to enter the code and stop the missiles from launching. The code is made up of four hexadecimal digits (0-9, and A-F).

In this game, the object for each level is to reach the opposite end of the level. For the first 5 levels, once you make contact with the Depo you will receive a random position of the code. It is possible to get the same position more than once. On the sixth level, once you reach the missile, you must enter the code as quickly as possible using the joystick, and press the button to see if it is accepted. If it is, you have saved the day, and the game begins on a harder level. If you don’t enter the correct code before the impact….

http://www.atariage.com/forums/topic/154189-failsafe-7800-wip/