Another unique take on the concept is combining non-linear branching storytelling with the concepts of time travel and parallel universes. Early attempts at such an approach included Squaresoft's "Chrono" role-playing game series (1995–1999) and ELF's visual novel ' (1996). "Radiant Historia" takes it further by giving players the freedom to travel backwards and forwards through a timeline to alter the course of history, with each of their choices and actions significantly affect the timeline. The player can return to certain points in history and live through certain events again to make different choices and see different possible outcomes on the timeline. The player can also travel back and forth between two parallel timelines, and can obtain many possible parallel endings. The PSP version of ' featured a "World" system that allows players to revisit key plot points and make different choices to see how the story unfolds differently. "Final Fantasy XIII-2" also features a similar non-linear time travel system to "Radiant Historia".