Space Invaders Galactica is a hack or modification of the original Space Invaders game. The 'galaxiaj' part might refer to a specific modification applied to the game. Hacks or modifications are fan-made alterations that change aspects of the game, potentially including visuals, sound, gameplay mechanics, and difficulty. This specific hack's details would need further investigation to uncover its precise modifications.

Space Invaders Galactica (galaxiaj hack)

Space Invaders DX (Japan, v2.1)