Space Invaders is a two-dimensional fixed shooter game in which the player controls alaser cannon by moving it horizontally across the bottom of the screen and firing at descending aliens. 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 towards 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 indefinitely.
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 projectiles from the aliens and player.
Popularized right after the release of the game, the “FURRER” trick allows you to get 300 points per mystery ship every time. It has to do with the way the random number generator works – at the beginning of every board count 22 shots whether you hit an invader or not. Wait for the mystery ship. Shoot once to hit it to earn 300 pts. Now count 14 shots. Wait again for the mystery ship. Shoot once at it for another 300 pts. count 14 shots and repeat for the rest of the level. once on the new level, start again at 22 and repeat to 14. This trick was invented by Eric Furrer who to this day holds the Stratford Record for non-stop Space Invadersplay — 38 hours and 37 minutes and an accumulation of 1,114,000 points 111 roll overs, averaging three rolls an hour.
Mystery Ship Shot Deflection: On the fifth wave of invaders, the second mystery ship will deflect your shot with the rarely heard “deflection shot” a shot played backwards.