Dougal Campbell's geek ramblings

Back in the 80s and early 90s, animated graphics were mostly very low-res. Computers and graphics cards just didn’t have the oomph needed to animate hi-resolution pictures with lots of colors, and they could only display 256 different colors on the screen simultaneously, indexed from a larger palette of available colors. But clever programmers realized that by modifying the index table, a sort of poor-man’s animation could be achieved. Some took this to a whole new level, creating motion and atmospheric effects that were quite impressive.

Old School Color Cycling with HTML5 | EffectGames.com