You fly a futuristic fighter craft called the R-9a -Arrowhead- (at the 22nd century), named for its shape, and because it is the ninth model in the 'R' series of fighter craft. The mission is to blast off and strike the evil Bydo Empire. Basically it's one where you shoot everything that moves - some things shoot back at you while others just get in the way and result in your death on contact. The scrolling background is a sort of cavern with ceiling and floor outcroppings in places, and these, needless to say, can also be crashed into. Some of the sprites are pretty big such as a giant spinning wheel monster type waiting near the end of level one. You actually have to get your ship inside it and shoot it in the eye to close its account. And I'm sure there are a lot of even bigger ... alien-monsters waiting on further levels! Quick clicks on the fire-button produce standard bursts of laser fire, but should you require a bit more firepower then hold the button down for a sec. You can see the nose of the ship collecting surrounding atoms of some description - then when you release the button again, a large fireball zooms out.
The Commodore port is an excellent example of a successful arcade conversion and technically is superior to its 8bit counterpart. The sprites themselves move beautifully and some of them are really big! The graphics are nice, colorful with most of the original details, while the sprites move smooth and fast. I really enjoyed the background scrolling which move smoothly in contrast to the incredibly choppy scrolling on the CPC (and MSX, ZX). Note though that, the MSX version is good too.
Sound here is one of its main advantages as it offers an awesome main menu and in-game tune, taken from the original (and also found on the Amiga versions) but no SFX. Note that the sound is poor on CPC series, being almost soundless, while the MSX version offers an in-game tune.