Trailblazer is an attempt to fix the perceived flaws in verison 3.5 of the d20 System that aren't being addressed by Paizo's Pathfinder RPG, while remaining backward compatible with the library of products available for both systems. The GM's Day Preview provided an immediately usable subset of the changes in the final product, addressing the following problems: the fragility of 1st level characters, the extreme nature of the power curve, the absolutes that grant automatic immunity or success/failure, the tendency to stop and rest after each encounter to restore hit points or magical resources, and a whole slew of more minor issues.