Planetoid is very similar to the popular arcade game. "Defender". For the uninitiated. it is set on a far off planet. where various aliens are doing their best to destroy the Humanoids, inhabitants of the planet. One set of aliens. the Landers, are trying to abduct the Humanoids from the bottom of the screen and take them to the top, when the Landers turn into Mutants, which are twice as fast, and twice as deadly.
You are the Defender, equipped with a ship armed with powerful lasers and "Smart Bombs" which will destroy all aliens on the screen. The mission is to prevent Landers from taking the Humanoids; at the same time fending off other nasties. You start with 3 ships and 3 smart bombs; an extra ship and smart bomb are given every 10,000 points. The game is over when all your lives are used up and then you can record your name along with your score in the Planetoid "Hall of Fame".
This game is written entirely in machine code and the speed and smoothness is stunning! The sound effects are also of a high standard and packaging is probably the best on the market. All these factors go to show that Acornsoft have set the standard in BBC games.