 "Space Invaders" became one of the first coin-op video arcade games to enjoy mega-success worldwide. Teen-agers and college students spent hours at the local arcade (or wherever one of the game machines was placed) using a single laser base trying to defeat an army of alien creatures who marched from side to side in grid-like formation, slowly but perilously approaching Earth. In 1980, Atari released a home version of the wildly popular arcade game for its popular home video game system. The format of the game was identical, this time with the laser base defending Earth against 36 of the alien creatures (arranged in a 6-by-6 formation). As in the arcade game, the object was to defeat the aliens before they reached Earth (with the aliens speeding up as they become fewer in number); allowing even one alien to land on the bottom row automatically ended the game, while losing three laser bases also meant the game over. On occassion, a spaceship would fly across the top of the screen, which the player could destroy for bonus points. If the player destroyed all 36 aliens, he was rewarded with a new army of 36 aliens, this time positioned one row lower than before. The Atari video game offered 112 variations, which determined everything from control of the missile, the number of players (up to 2), whether the protective shields remained stationary or swayed, if two players moved separate laser bases simultaneously and teamwork for various laser base functions.