GNU Dr. Geo is an interactive geometry software that allows its users to design & manipulate interactive geometric sketches, including dynamic models of Physics. It is free software, created by Hilaire Fernandes, it is part of the GNU project. It runs over a Morphic graphic system. Dr. Geo was initially developed in C++ with Scheme scripting, then in various versions of Smalltalk with Squeak, Etoys for One Laptop per Child, Pharo, then Cuis-Smalltalk.