As I covered in my previous post, I've been working on a retro-clone of the original 1974/1975 era Dungeons & Dragons rules titled The Fantasy Game. That post describes the first book, the Basic Player Guide, which covers rules for character creation, combat, magic, and exploration, which is roughly equal to Men & Magic, volume 1 of the three LBBs (little brown books) in the original boxed D&D set.