Instructions
Access the hidden minigame by navigating to the "Start" menu and pressing the "R3" and "L3" buttons on the controller repeatedly. As soon as you break free from the chair, walk over to the computer in the back of the room and press "X" to log on to the computer. Type "DOA" into the computer to access the Dead Ops Arcade hidden game.
Move the character with the left stick and shoot by moving the right stick. Spin 360 degrees while shooting to take down enemy zombies that surround you.
Progress through the first 39 levels of the game to reach the final stage and boss. You can use the available boosts and power-ups that you collect during gameplay to help advance through the levels. For instance, press the right trigger to initiate a speed boost and bust through zombie enemies. If you collect a nuke, press the left trigger to detonate it when you are in danger of being completely surrounded by enemies.
Defeat the "Cosmic Silverback" boss in level 40. Keep away from his lunging attack and continually shoot him from a distance to complete the level. You will enjoy a small cut scene and be returned to the first level of the game. Back at the first level, you will still have all the power-ups you accumulated and will be able to continue playing through the same levels.