From Starfire Design Studio
PDF – $19.99 USD
Ultra Starfire is the 5th edition of the Starfire system. Started in 2003, Ultra Starfire was designed to be fully balanced for player-versus-player combat, with the goal of building a 4X campaign system that could potentially be used for tournament game-play. Ultra Starfire had several updates to improve the balance and game-play over the next half a dozen years, and remains as the only edition of the Starfire rules with a focus on balanced PVP campaigns.
Note that Ultra Starfire is a group of 36 PDF files zipped together, one for each chapter of the book, with rules cross-linking as long as the PDF files are all in the same folder.