Originally Atomic Pinball was a platformer. It was actually quite interesting, as it had an unusual character (an atom) with some decent movement mechanics and unconventional obstacles. Unfortunately, one of those obstacles specifically worked very badly.

Observe this random platformer (or something) image from the media library:

As you can see, to get anywhere the player must move through air. Unfortunately, when you are a hydrogen molecule, each oxygen molecule is 16 times heavier than you and if given energy may also cause you to explode. In the platformer, you never really got to wherever it was you wanted to go before some giant bloody wrecking ball knocked you right back to where you started. More thought is needed to turn this from an awfully inconvenient issue to a fun game mechanic.