The Big Robot website offers Permutation Racer, a free game for Windows and OS X from the developer of Sir, You Are Being Hunted. This was developed as a procedural generation prototype, and here is what it includes: "In Permutation Racer you race against the clock to reach checkpoints, collecting stars (you can jump, don’t forget) and avoiding barriers or red spikes. Because it’s all mathematically generated, every track is different. This is just a prototype, so it’s very simple, but we think you’ll enjoy it. You might even recognise some of the procedural geometries from other images we’ve posted from our Lodestone project." Thanks PCGamesN.