This is a game designer's game. It has a flawless, timeless perfection, right up there with Tetris. This is not a puzzle game, though. It's a tight, twitchy game about perception and nerves, with a bumping soundtrack worth the price of admission by itself.
You are a triangle in the center of the screen, rotating around a hexagon. The only keys required to play the game are left arrow and right arrow. You move at one speed: fast. So the moment and amount of time you press provide all the challenge.
The screen is divided into light and dark sections that radiate from the points of the hexagon. Walls stretch across a section or multiple sections. When you start a game of Super Hexagon, the walls start closing in toward you. If one hits you, game over.
But there's always a way out. You navigate a kind of maze by dodging the walls coming toward you in their multifarious configurations. With practice you can get the timing down and get around a few walls, no problem.
Then the hexagon distorts, and starts throbbing in time to the music, and the screen starts spinning, and flashing, and changing colors, and other tricks that are similarly hard to notice because it's all happening so fast.
Prepare to be punished.