Metal Gear Solid 2: Sons of Liberty is a stealth action game directed by Hideo Kojima, developed by Konami Computer Entertainment Japan and published by Konami for the PlayStation 2 in 2001. It is the fourth game in the Metal Gear series produced and directed by Kojima and is the direct sequel of Metal Gear Solid. Its release was followed by an expanded edition, Metal Gear Solid 2: Substance for the PlayStation 2, Xbox, and Microsoft Windows. Metal Gear Solid 3: Snake Eater, a prequel to the entire Metal Gear series, followed in 2004. In 2008, a direct sequel, Metal Gear Solid 4: Guns of the Patriots, was released. The game was well-received, shipping over 7 million copies worldwide. It received a metascore of 96 on Metacritic and average of 95.09% on GameRankings. While the gameplay and graphics were universally acclaimed, critics and fans were divided on the philosophical nature and execution of the game's storyline, which explores the themes of memes, social engineering, political conspiracies, and artificial intelligence. Critics and fans were also divided on Raiden, a new character who serves as the main protagonist for the majority of the game, and the length of the game's cutscenes. Over the years, the game has seen greater acclaim.