Tom Clancy's Splinter Cell is a series of stealth action-adventure video games, the first of which was released in 2002, and their tie-in novels that were endorsed by Tom Clancy. The series follows Sam Fisher, a highly trained agent of a fictional black-ops sub-division within the NSA, dubbed "Third Echelon", as he overcomes his adversaries. Levels are created using Unreal Engine and emphasize light and darkness as gameplay elements. The series has been positively received, and was once considered to be one of Ubisoft's flagship franchises, selling more than 31 million copies by 2011. No further installments have been released since 2013, though a VR version and a remake of the first game have since been announced. Games Tom Clancy's Splinter Cell (2002) Tom Clancy's Splinter Cell was developed over a period of two years and developed by Ubisoft Montreal with original publishing by Microsoft Game Studios for the Xbox as an exclusive title. Later in 2003, Ubisoft ported the game to Microsoft Windows, Mac, PlayStation 2, GameCube, and Game Boy Advance. Inspired by the Metal Gear series, it uses an Unreal Engine 2 that was modified to allow light-and-dark based gameplay. Tom Clancy's Splinter Cell: Pandora Tomorrow (2004) Pandora Tomorrow was developed by Ubisoft Shanghai and Ubisoft Milan and introduced multiplayer gameplay to the series. In single-player mode, the game AI adapts to adjust to the player's skill level. Unlike other games in the series, which generally lean towards information-based threats, the plot of Pandora Tomorrow focuses on biological warfare, in which an Indonesian terrorist group threatens to infect people with the smallpox virus. Fisher is also given new abilities like SWAT turns and whistling to attract enemies' attention. Tom Clancy's Splinter Cell: Chaos Theory (2005) Ubisoft Montreal and Ubisoft Milan were again responsible for the third game in the series, Chaos Theory. It adds a cooperative multiplayer mode. Originally announced to be released in Fall 2004, its initial releases were made at the end of March 2005. The Unreal Engine was heavily modified, this time from version 2.5. The game includes a number of new features, including adding a combat knife to the player's inventory. Maps are also more open with multiple ways of achieving the end goal. Tom Clancy's Splinter Cell: Essentials (2006) Essentials extends the Splinter Cell series to the PSP platform. Through a series of flashback missions, the player learns more about Fisher's backstory. The