Space Invaders  is an arcade video game  released in 1978.  

Space Invaders is one of the earliest shooting games, and the aim is to defeat waves of descending  aliens with a laser cannon to earn as many points as possible.   The aim is to defeat five rows of eleven aliens—some versions feature different numbers—that move horizontally back and forth across the screen as they advance toward the bottom of the screen. The player defeats an alien and earns points by shooting it with the laser cannon. As more aliens are defeated, the aliens' movement and the game's music both speed up. Defeating the aliens brings another wave that is more difficult, a loop which can continue without end.
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The aliens attempt to destroy the cannon by firing at it while they approach the bottom of the screen. If they reach the bottom, the alien invasion is successful and the game ends. A special "mystery ship" will occasionally move across the top of the screen and award bonus points if destroyed. The laser cannon is partially protected by several stationary defense bunkers—the number varies by version—that are gradually destroyed by a numerous amount of blasts from the aliens or player. A game will also end if the player's last laser base is destroyed.

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