RPJ Core is a generic tabletop roleplaying engine. Rather than provide rules for every circumstance¸ it pushes some implementation details down to modules¸ complete games which build on top of it. Philosophically¸ RPJ charts a course between narrative and simulationist games¸ blending elements of both. Players have tools to affect the fiction when it clashes with their character concepts¸ and gamemasters have options to abstract conflict when the detailed rules don't capture the drama. At the same time¸ a traditional skill-based design under the hood permits gamemasters to zoom in on tasks which require detail. This is a prerelease product. Major rules changes are unlikely¸ but still possible. Key Features Level-less¸ skill-based character system RPJ characters are the sum of their skills: given proper investment¸ any character can be good at anything. At the same time¸ a lightweight character class system helps to guide and focus character builds. Streamlined combat and damage Combat occurs in a gridless framework based on large regions¸ using a simple adjacency system to determine who is close to whom. Damage is resolved using a saving throw system: when receiving damage¸ characters roll to shrug it off. Modern ranged combat rules An optional system for cover¸ suppressive fire¸ and more fills in the gaps for combat using firearms and other modern and futuristic weapons. Magic¸ conditions¸ and more Extensibility is a central RPJ design goal. Not only does it leave room for modules to implemnt their own systems¸ it provides some example optional mechanics suitable for cribbing¸ including two options for magic and special abilities¸ along with streamlined¸ genre-agnostic money and inventory systems. Permissive licensing RPJ's core mechanics are provided under the Creative Commons Attribution-Sharealike-Noncommercial license¸ so that they remain freely available to all. Its optional mechanics¸ however¸ are provided under the Creative Commons Attribution license¸ so that they can be readily copied¸ remixed¸ and included in commercial products.