SOS (エスオーエス, Esu Ō Esu) is a shoot-em-up arcade game released in February 1980 by Namco. It is the third and final game in Namco's series of monochromatic games, and is the first Namco game to feature a coffee break between levels.
The player uses the joystick to move the "Shinryaku plane", and press the fire button to shoot a bullet.
The game goes on forever on one level: enemy planes come down towards the screen, and the player shoots bullets to destroy them for 10 points. The player can only shoot one bullet at a time (similar to the company's Galaxian and Navarone), and the bullet must be off-screen before another can be shot. If the player shoots a bullet when the Shinryaku is moving, that bullet will move in the opposite diagonal direction of the player.
If 100 enemy planes pass the player, the game is over, regardless how many lives the player has.
Occasionally, a morse-code SOS signal will appear, and the amount of planes that have passed the player will be reduced by 9, but if the amount of enemy planes is 9, it will do nothing.
The player's ship can be destroyed by an enemy explosion: this can be irritating for players that can't get away in time. It makes it more difficult that the player moves slowly across the screen.
Coffee Break Edit
If the player earns 2000 points, then a coffee break will occur, and will show a girl in a bikini with an eyepatch. If the arcade owner has the nudity DIP switch set to ON, then the girl will be topless after 6000 points, and completely naked after 10000 points. This is Namco's first game that isn't suitable for all ages; eight years before the company's Splatterhouse in 1988.