Chronotron is a time based puzzle game. Replay history and manipulate the environment to get the key and escape the level.
On the surface Chronotron is a standard platform game, however each level must be played multiple times with you completing the correct moves in advance to enable future versions of yourself to complete the puzzle.
For example in one level you are presented with a high wall and a crate. Standing on the crate alone is not enough so you pick up the crate and wait patiently for a few seconds. Go back to the time machine and you will reappear... twice. One version of you repeats your last movements, the other version is controlled by you so you can now go and stand on the crate that is being raised by your past self.
Confused? It's actually a very simple mechanic executed really well. Playing the game will make everything clear, but it's only really good for those who enjoy lateral thinking as the puzzle quickly become quite challenging.
If I was to judge it based purely upon it's platforming merits then it would be scored quite low - the controls are a bit twitchy and there is no Mario style momentum, however coupled with a basic physics engine and a clever gameplay system Chronotron works very well indeed.