portal 2 : single player at least 10 hours

In comparison to the first game, which was bundled as part of the Orange Box alongside Half Life 2 and Team Fortress 2, the second game is considerably longer, running at somewhere (for us, at least) between ten and eleven hours.

The first game took about three and a half hours to get through, which puts Valve�s claims of the sequel being around two to three times longer at almost pinpoint accuracy.