Bounce on floating boulders, higher and ever higher, to avoid the ever increasing flames.
This may have been one of the first freeware games I ever played. It wasn't very good back then, either. Right now its getting a review purely for nostalgia, so skip over it if you're not interested.
It was a few years ago and somehow a little game called Alex the Allegator popped up, and changed the way I thought. A whole game? For free? Years later, here I am. Hundreds of freeware titles later.
At the start, tracking down games was difficult, so I followed the lead Alex set and came across other low colour games. This was one of them. It centralises around a sphere who goes up a cave. The cave is filled with boulders which float. Across the edge are pointy rocks. They all, regardless of their angle or substance - bounce you upwards. The more bounces, the higher you go.
Along the way, the odd cave-in will happen (fortunately that is always neatly executed for easy avoision) interspersed with a stick of dynamite flying down the shaft.
If you've read this far, you might as well give it a go, but don't expect to be thrilled. Its a simple game in absolutely every single sense of the word.