Steve Coleman‘s Rainbow Walker was first published by Synapse Software in 1983.
It is an unusual, pseudo 3D platform game with a curved track of grey tiles, each of which you (a small, blobby character called Cedrick) have to step on in order to turn into coloured tiles. The aim being: to turn the entire track into a rainbow, by standing on every tile.
If you fall off the track you lose a life. If you are carried off by a patrolling bird you have to start the level from scratch (annoying, but you can learn to avoid them). Other meanies and traps make it hard for you too. In fact: Rainbow Walker is quite challenging, which makes it very good.
A hidden gem on the Atari 800, if ever there was one. I didn’t even know about the game’s existence until recently, and was pleasantly surprised when I played it. For 1983, this is a brilliant piece of coding and design work.