Galaga

Galaga was created in 1981 by Namco. This game, like Space Invaders, is simple. The object of the game is to blow up all of the enemies. You are a space ship with unlimited ammunition. The enemies come flying on to the screen, at which point you can start shooting away. The enemies can drop things down at your ship so you need to maneuver around everything. You have three lives to spare - don't waste them!

1. neave.com

2. Spaceinvaders.de/

3. Freespaceinvaders.org