The game harbored many gameplay revisions, such as the series-unique ability for the player to move about before the round begins and the introduction of walled stages.[5] However in recent years, Tekken 4 has recovered to the point of being widely praised, and this is largely for its innovation in gameplay, atmosphere, and attention to detail.[18] The game engine had been tweaked to be more focused on the environment, causing the characters to move more slowly and fluidly than in Tekken Tag Tournament.[19] Finally, the game introduced a brand new graphics system, that featured increased lighting, dynamic physics, and smoother surfaces.[26][27] The arcade version features a total of 21 characters, consisting of 16 returning and 5 new ones, including the Irish-English boxer Steve Fox who is revealed to be the son of Nina Williams.^a Unlockable character ^b Only playable in console version (makes a cameo appearances in arcade version) ^c Skin/palette swap ^d Skin/palette swap when Lee Chaolan unlocked Two years after the King of Iron Fist Tournament 3, Heihachi Mishima and his scientists have captured samples of Ogre's blood and tissue to splice with Heihachi's genome, to make him immortal.[30] In an attempt to lure Kazuya and Jin out, Heihachi announces the King of Iron Fist Tournament 4, with the ownership of the Mishima Zaibatsu being the top prize.[56]IGN's Jeremy Dunham noted the walls and confined spaces as "probably Namco's wisest decision," and called the game "a solid fighter in every sense of the word.[63] It was considered the most serious and one of the darkest tales in the Mishima Saga, without completely abandoning some comical relief characters such as Kuma and Marshall Law.[64] Together with this was the tone and atmosphere, which features known classic songs such as the jazz track ‘’Bit Crusher’’ at the actual Shinjuku crossing stage, airplane mixed electronic song ‘’Touch and Go’’ at the Philadelphia airport stage, and piano-grunge themed ‘’Authentic Sky’’ at the Tokyo building rooftop, among others, that added a strong atmospheric feel to the game that has never been explored in an artistic manner before.[67][68][69][70][71] The artwork and the grunge theme, mixed with electronic-jazz music and gritty tones helped improve the visual aspect of the game design as well.have noted the innovations introduced in Tekken 4, such as interactive environments in stages and the first full-use of voice acting and win pose animations in fighting games.[77][78][79] The praise for the story, music, atmosphere, and character development, as well as having the rawest and most serious tone in the series, has gone on to grow significantly in acclaim over the ensuing decades.