Dynasty Warriors 4 (真・三國無双3, Shin Sangokumusō 3, Shin Sangokumusou 3 in Japan) is a hack and slash video game and the fourth installment in the Dynasty Warriors series. Dynasty Warriors 4 was developed by Omega Force and published by Koei. The game is available on PlayStation 2 (PS2) and Xbox and is based on a series of books called Romance of the Three Kingdoms, written by Luo Guanzhong. As the series has progressed, it has strayed further from the actual plot of Romance of the Three Kingdoms but instead has given the user more input on how the storyline progresses. When it was released in Japan as Shin Sangokumusou 3, it topped the sales charts, sold over one million copies within nine days, and received an average of 78 out of 100 on Metacritics reviews. Originally released on the PS2 in March 2003, it was later ported to the Xbox in September of the same year and, in 2005, ported to the PC under the name Dynasty Warriors 4 Hyper. Two expansions were released for the PS2 version of the game, Xtreme Legends and Empires. Whereas Xtreme Legends requires the player to use the original Dynasty Warriors 4 disc to access all of its features, Empires is a stand-alone game that can be played without the original disc. The game is the first in the Dynasty Warriors series to introduce an Empires expansion pack and the second to include an Xtreme Legends title. These expansions are not available for the Xbox version of the game.