in 1990s, game creation systems for the ibm pc shifted both to the more general and the more specific. whereas frameworks like rsd game-maker and klik & play attempted to accommodate any genre, communities grew around games like "zzt" (later, megazeux) that permitted such extensive user modification that they essentially became de facto game creation systems. pie in the sky software created a full on 2.5d first-person shooter creator out of an engine they previously used internally, which sold in three total versions until 2003.