"Radiant Historia", released by Atlus for the Nintendo DS in 2010, combined the gameplay of traditional RPG titles with a highly tactical grid combat system, with several unique features such as a queue allowing party members to switch turns and perform combo attacks when near each other on the queue, and the manipulation of enemy positions by knocking a target onto another grid space and attack multiple targets when enemies fall onto the same grid space. The game is most notable for its unique take on the concept of non-linear branching storylines, which it combines with the concepts of time travel and parallel universes, expanding on the "Chrono" series. "Radiant Historia" takes it much 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 having a major effect on 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. Square Enix's PSP version of "", released around the same time, featured a similar "World" system that allows players to revisit key plot points and make different choices to see how the story unfolds differently.