Phantasy Star Online Blue Burst, a port of the Xbox version, was released for Microsoft Windows in 2004 through digital distribution, featuring both Episode I and Episode II, and adding a new Episode IV, NPCs, quests, team system, and server-side saving system. The Phantasy Star Online titles are a sub-series of Sega's Phantasy Star series of games that began in 1987. With the exception of Episode III, the PSO games themselves are hack and slash role-playing games where the player slays monsters, levels up, buys new equipment, etc. The online Phantasy Stars differ from the previous games of the series by offering a real-time – rather than turn-based – approach to combat, seamlessly integrating this with exploration and plot developments.