This game is Livewire's unlicensed implementation of the classic Space Invaders.
Of the different formats, the C64 version has graphics closest to the Taito original, though it only has 8 columns of invaders. The Vic 20 version also has graphics similar to the original and has 9 columns of invaders, but only 3 bunkers rather than the 4 in the original. The MSX version has the same 11 columns of invaders as the arcade original, but the graphics for the aliens are different. The Plus/4 version is the furthest away from the arcade original with 8 columns of a single type of invader, the graphics for which change in subsequent waves.