Taito's 1978 arcade hit can be enjoyed on the Atari 2600 with 112 different variations. Space Invaders has you steering a laser cannon on the bottom of the screen while trying to blast rows of alien invaders. These aliens will move from left to right and then down one row once they reach the edge.They will continue their march from right to left, repeating the pattern until they reach the bottom of the screen, thus ending the game. Not only must you blast the aliens before they land, you'll also have to avoid their laser bombs! Fortunately, there are three shield barriers between you and the invaders, which will provide you with limited protection. "Limited" is the operative word, since the shields eventually disappear with repeated hits!Shooting aliens (there are six varieties, one for each row) will earn you points, ranging from five to thirty depending on their initial location. The rate of the aliens' movement will increase as you eliminate them from the screen, and subsequent waves will start the aliens closer to your laser blaster.The Atari 2600 version differs from the arcade game by offering six rows of six aliens instead of the original's five rows of eleven. Some of the variations include moving shields, zigzagging laser bombs, two-player cooperative play and even invisible invaders. Watch for the Command Alien Ship moving across the top of the screen; if you shoot it, you'll receive 200 points.