 "SimCity" uses a new engine called GlassBox that allows for more detailed simulation than previous games.Throughout its development, "SimCity" received critical acclaim for its new engine and reimagined gameplay; however, publications cautioned the game's use of a persistent Internet connection, with which it stores saved games and allows players to share resources.Prior to release, "SimCity" received positive reviews; however, the game's launch was received negatively due to widespread technical and gameplay problems related to the mandatory network connection for playing and saving game data.