Hydra Slayer is a Roguelike game focused on one thing: slaying Hydras. It features a unique (AFAICT) gameplay mechanics (although the main idea is based on old mathematical puzzles). To defeat a Hydra, you have to choose your attacks carefully, just bashing it with your "best" weapon is not likely to be a successful strategy. To win the big game, you have to choose your set of weapons wisely, and use your resources efficiently! The current version (13.0) has been released on Nov 22, 2011.