MOOSE Crossing was an educational MOO (a type of MUD, a text-based virtual world) developed by Amy S. Bruckman in 1996 as her doctoral dissertation work. It employed a constructionist learning pedagogical approach and was designed for teaching children 9 to 13 years of age. Bruckman's work on MOOSE Crossing and MediaMOO was called "the most notable MOO research in education".