Zektor

Zektor is a multi-directional shooter arcade game that was released by Sega, in 1982; it runs on their G80 Vector hardware, and was licensed to Gremlin Industries for US manufacture and distribution as it is based on their own Eliminator, which was released in the previous year. The player must take up control of a ship on a mission to free eight cosmic cities, that have been conquered by aliens - and in order to do so, you will have to fight off three individual waves of "Fighters" and "Robo-Probes" which are often shielded in red. Each hit on them will reduce the shields' strength, until they disappear, then your next shot will kill them; and there are also three different types of "Moboids" to watch out for (the green ones will cause your ship to spin around and enemy ships to bounce off them on impact, while the blue ones will cause all ships to bounce off them, and the red ones will kill all non-shielded ships, including that of the player). After you have defeated all three waves of the current city, the alien who is holding it will appear, with a barrier of revolving rings around him (or her) - and you will have to fire a well-placed shot through the rings to kill the alien before he (or she) escapes in order to receive an extra life and proceed to the next round. The eighth city's alien is also that one-eyed one from Space Fury; once you have defeated him, the eighth round will repeat indefinitely (until you run out of lives).

There are also hidden letters in each of the eight cities; it is not known what they mean, but it can be speculated that they are either the designers' initials, or part of a secret code from the programming.