Released in 1981 by Midway.
Gorf has 5 distinct levels. Once completed you're promoted to the next ranking. After completing 6 loops and reaching Space Avenger, you've essentially beaten the game on its highest difficulty. I managed to complete 8 loops before being vanquished by the "Galactic Orbiting Robot Force".
A great game without question, which also utilises the same Votrax speech synthesis as Q*bert.
