Many modern games, from FIFA to Doom, have been around long enough to have actual retro versions lurking in the archives.
But others, including current chart-toppers Call of Duty: Black Ops II and Halo 4, haven't quite got the heritage to have been based on 8-bit classics.
Luckily those games do have a lot of fans, many of whom are apparently very skilled with game design and 8 bit graphics, and have a lot of time on their hands.
As a result,old-fashioned versions of modern video games are everywhere online - and we love seeing how our modern favourites are re-imagined for low-res monitors, tiny processors and 2D platform mechanics.
Check out Call of Duty Retro and our other favourite 8-bit games in the slideshow below.