The command set in Moi3D seems to strike a good balance between providing needed functionality and composibility of the included feature set. In this example of tween, there is something more informative about seeing the actual way in which this command is likely implemented elsewhere ( e.g. Rhino ) by having to "pipeline" the sequence of commands than choosing a single command that hides what is happening. Unlike my typical experience when learning a new domain, the Moi3D interface is helping me to learn the fundamental constructs of NURBS modeling. I think this is also due in part to the user interface of Moi3D which I find very good. Appreciatively