Decimation is my entry for the 2009 7DRL Competition.
It's a roguelike game where you're the number zero and your goal, in zero's naturally nihilistic fashion, is to wipe out all the other numbers! But you have to use mathematical operations in order to make them equal zero...
I wrote Decimation in C# using Windows Forms, so you'll need the .NET Framework to run it (it might also run under Mono; I haven't tested that yet.)
Download the game here! Or grab source code or look at a screenshot.