Though this game is named Galaxian, it has nothing to do with the original Galaxian arcade game.

It's rather a clone of the arcade game Moon Cresta by Nichibutsu, released in 1980.

Using your space ship weapons, you have to destroy 4 alien waves comming at you. The circular movements of the invaders is typical of Moon Cresta. Even the introduction tune is the same as the original arcade game.

After defeating the 4 levels, you get a docking sequence just as in Moon Cresta. Indeed you have to maneuver your ship back to the mothership and dock to it. But unlike the original game, to reach your goal you have to cross an asteroid field without crashing by adjusting your speed and movements.

This last level is thus rather inspired by Taito arcade game Lunar Lander released in 1978.