From the Book's Introduction: The Four Color to Fantasy rules fit perfectly with the core d20 System rules, allowing you to play a medieval-style superhero game. You can also use the core rules to simulate different genres (modern day, futuristic, pulp) simply by changing a few details. Often all you need to do is remove or restrict spellcasting classes and incorporate appropriate weapon and armor rules. Core Rulebook II contains rules for varying your campaign style to fit different time periods, including stats for handguns, grenades, futuristic ray-guns and so on. In some ways, this can actually be beneficial, because many superheroes use weapons common to fantasy settings, and many of the staple monsters of a fantasy bestiary would make perfect foes for super-powered heroes. We even include a new class in this book, the Specialist, which represents more mundane characters, who rely on knowledge, education, or training, like real-world people. With just the Fighter, Hero, Rogue, and Specialist, you can easily create heroic characters for the modern day, without needing anything beyond the core rules and this book. However, you may choose to use another rule-set for your game. The most common superhero tales are set in the modern age or in the near future. For these games, we recommend that you use one of the modern d20 system games or settings that are available. You’ll find d20 games and settings out there based on modern-day spycraft, on 1930s pulp, or on futuristic fantasy. Regardless of what ruleset you prefer to use, as long as it uses the d20 system rules as its basis, you should be easily able to add the rules from Four Color to Fantasy.