Space Fever

Space Fever is a Nintendo developed video game in the same vein of Space Invaders in regards to gameplay mechanics and the overall concept. Its a blatant ripoff released in 1979 for arcades that had various different versions, including one that was in color (the original wasn't).

Gameplay
The game is nearly identical to Space Invaders. In Space Fever, aliens of different designs (and different colors in the colored version) start to come closer and closer to Earth. Every once and awhile a UFO will pass above, just as they did in Space Invaders. Four blocks guard you from the the alien invaders, and it's best if you use your tank to shoot a gap in the blocks and shoot the aliens from there, though if you wish you can do so by other, more apparent means. The game has three versions, each featuring different ways the aliens move, which distances itself slightly from Space Invaders, which did not have this feature.