The Sims Stories is a series of video games from The Sims series released in 2007–2008 based on a modified version of The Sims 2 engine. The modified game engine is optimized for play on systems with weaker specifications, such as laptops. As such, its system requirements are lower than that of The Sims 2, but it can still be played on desktops. The series is introduced mainly for three segments of the market: those who wish to play The Sims 2 on their laptops (which usually have lower specifications); those who wish to engage in other activities such as instant messaging while playing the game, and; those who are new to the franchise. In addition to a Free Play mode with classic, open-ended gameplay, the games contain a structured, linear Story mode where players are required to complete a series of goals to progress in the storyline. While Life Stories and Pet Stories each contain two separate stories, Castaway Stories contains one story that is double the length of any one story in the first two games. As an introductory series, major features are removed or modified from those in The Sims 2. For example, fears are completely removed in all three games, and the elder life stage is completely removed in Pet Stories. Officially, the save files from this series are not compatible with the main The Sims 2 games. However, players have experienced success in adapting some files.