Geometry Wars: Retro Evolved was released originally as a mini-game within Project Gotham Racing 2 for the Xbox. Chances are good that you’ve played at least one iteration of GeoWars. However, you may not have known that it is available on the PC, and for less money than anywhere else.
The premise is simple: shoot the shapes. Also, try not to slip into epileptic seizures. You play by moving an androgynous spaceship-like entity around a grid, all the while attempting to avoid as well as destroy any shapes that come flying at you. Collide with a shape and you die. As time goes on, you rack up points and the game becomes increasingly hectic. Extremely hectic. I find the game to be very difficult, but that doesn’t keep me from coming back to it from time to time. It also won’t keep me from recommending it to you. Even if you suck at it, you’ll have fun with it. It’s worth every penny.
Geometry Wars: Retro Evolved can be purchased on Steam for $3.99. Alternatively, it can be purchased on Xbox Live Arcade for 400 Microsoft Points ($5), or played through Project Gotham Racing 3 on Xbox 360, which I would imagine could be found for fairly cheap by now.