Nintendo began experimenting with 3D technology in the 1980's, and began the development of a 3D gaming system in the mid-90's. They even developed one game, 2001's Luigi's Mansion, to be played on a 3D television. However, due to the high cost of the technology at the time, it was decided not to include the feature. Gunpei Yokoi's continued work at Nintendo into 2006 kept enthusiasm for 3D technology alive at Nintendo. Even before his retirement, work began on a new system that would revolutionize how players navigated 3D environments.