 Portal 2's lead writer Erik Wolpaw estimates each campaign to be about six hours long. Portal 2 contains in-game commentary from the game developers, writers, and artists. The commentary, accessible after completing the game once, appears on node icons scattered through the chambers. According to Valve, each of the single-player and cooperative campaigns is 2 to 2.5 times as long as the campaign in Portal, with the overall game five times as long.
