Bit Fortress is a vertical shooter created by Davioware in under eight hours, featuring epileptic-inducing graphics and a catchy background tune. There is only one level to play in this build, but it comes complete with a boss battle at the end and will loop from the beginning once you've managed to beat the game.

Developed using the Construct game creation engine, so you might need to update your operating system with the latest version of DirectX to get it working. You can quit the game at any time by pressing the left Alt and F4 function key. (source, forum thread)