From the inlay:
Use extreme force to protect your space cows from marauding mutants.
In game text:
The Game. You and your amazing ship Badjak must protect the oxes from being taken away by the naughty aliens. Survive the nine zones in each of the eleven planets to win.
The Story. In one million AD oxes are very expensive and are guarded against alien rustlers by you. Kill them to stop their illegal trade. After all its only a game.
The Aliens come in all shapes n sizes. Some pinch your oxes. Some give you bonus oxes. Some hyperspace you abit. Others just bother you and a few even reproduce.
Oh No! is a top-down shoot-em-up written by Chris Yates, with some resemblance to a cross between Sinistar and Defender.
The player controls a ship which can move in eight directions. The playing area is larger than the screen and a radar screen shows enemies and the 'oxes' your ship is protecting. These appear as coloured gems on the screen. Enemy ships attempt to steal the gems and transport them off the edge of the map. Your ship can shoot a ship carrying an ox and it will be dropped. If all the oxes are stolen the game is over.
Your ship has two weapons, fired simultaneously. The first is a basic blaster which fires in the direction that the ship is pointing. The other appears as a boomerang which homes in on enemies.