This game is an unlicensed version of Asteroids.
From the inlay:
You are the only person who has flown the Svlegian Raider. You sit back, the seat moulds around you and you blast towards the alien asteroids.
Suddenly they are upon you, you thrust at them, dodging, swerving and firing Phaser Beams at them. They come at you again and again. Still you fire, wiping them from the skies...
You keep firing as they drift towards Nolveg, you fire again...
This game is loosely based on the arcade classic "Asteroids", though it does not feature flying saucers, just the eponymous Asteroids.
Like many Quicksilva games for the ZX81, the game is provided with a list of POKEs which can be used to modify parameters such as the number of lives and at which level bonus points are scored, etc.
On the basic ZX81, the player's ship is represented by a number. The number indicates in which direction the ship is facing. 0 indicates straight up, 1 indicates diagonally up and right, 2 indicates right, etc. Asteroids are represented by blocks.
However those with a QS Character Board peripheral could load alternative characters in place of the ZX81s standard character set. Some editions of this game included an additional file with characters representing the player ship facing in each of the 8 directions, and detailed graphics for the asteroids.
The outside of the inlay states "For the ZX-81 with 16K RAM" however the instructions state that the basic game "consists of 3K of Machine Code".