Creeper World is the most popular game by Knuckle Cracker, a software project managed by virgilw.
Creeper World is a new take on Tower Defense games. Instead of many enemies confined to a trench, Creeper World involves one enemy that freely covers terrain, "creeping" towards your base. Forget all that RTS nonesense about gathering resources and finding new ones, the economy of Creeper World runs purely on energy, the more energy you have the more you can spread out and the more turrets you can safely field. There are several buildings which each have a unique purpose and are all useful as well as several turrets each with their own reason for being, you'll never find yourself favouring one building or turret over any other in any balanced map.
On each map your objective is to hold the creeper back from detroying Odin City, your home base, while you move quickly to secure a number of Rift Totems and connect them to Odin City. Once these totems have been supplied with energy they open up a Rift which allows Odin City to escape, thus winning you the map.