From the introduction: Welcome to the Dice & Capital Dice (DxD20) role-playing game system. This comprehensive, scalable rule-set is meant to accommodate any and every genre of game-play, from prehistoric tribes to planetary starships, with options for magic, psionics, super-powers, and heroics in-between! Consisting of three main rule books, the DxD20 system is also meant to be backwards-compatible, easily incorporating all 3.5 OGL-compatible products such as D&D 3.5, d20 Modern, d20 Future, and more, thus making everything old new again. ... The rulebook for creating your character, with 40 character classes, and over 75 skills, 200 feats, and 300 spells and powers to choose from, the DxD20 Hero's Handbook opens the door to limitless role-playing possibilities!