Alien Raiders

Alien Raiders is one of the two Microvision games released in 1981. It is a fast-paced action game set in space where the player fights alien raiders to prevent them from landing. Originally designed as a Space Invaders game, Milton Bradley did not like the licensing deal and altered the game to make it have different gameplay.

Alien raiders appear at the top of the screen and move horizontally from the right to the left, towards the player's landing area. The player can manipulate a firing beam. It consists of a single square that moves vertically at the left side of the screen automatically and at a fixed speed. The player cannot exercise any influence over the speed. By pressing one of the three buttons labelled with an arrow and the word "fire", the firing beam is activated. It extends to the right and can take out raiders when the player carefully times both the horizontal and the vertical position. Raiders can however only be hit when the tip of the beam is directly on top of a raider or on the square immediately to the left of it. To determine the distance of the firing beam, a control knob at the bottom of the device needs to be manipulated. Turning the knob clockwise lengthens it, turning it counter-clockwise makes it shorter.

The player only has a limited amount of fuel and firing the beam depletes it. It uses less fuel when it is fired when a raider is nearby, but that allows the raiders to approach towards the landing area and leads to a higher risk. The final goal is to get a score a high as possible before the raiders reach the landing area or all fuel is gone. Since some raiders have different speed, it is also possible to wait until two of them overlap and take them out with a single shot for an economic use of fuel and twice the regular amount of points. It is possible to hold down the fire button as a last resort to take down many raiders at once, but this costs large amounts of fuel.

Two types of games are available. In Game 1 four raiders appear - three slow ones and a fast one - and three points are awarded per defeated ship. As soon as a raider is destroyed, a new one appears. Game 2 is similar with four raiders at the start, but more raiders appear simultaneously after a while (up to five or six at a time), they gradually become faster and they are worth more points over time. In Game 1 there are 150 units of fuel at the start with a 120 unit bonus after every eighth raider shot down. In Game 2 the player starts with 75 units and receives 60 bonus units for every eighth raider. The amount of fuel that can be held is capped at 255 units. Next to the two types of games two skill levels can be chosen. These only influence the speed of the raiders.