Sutherland saw, very early, that a constraint system was the way to go. We went through generations of CAD systems and draw programs which didn't do constraints. Even today, most draw programs don't do constraints as well as Sketchpad.
Sketch mode in Autodesk Inventor does constraints very well, including difficult geometry problems like circles tangent to other circles. This is a solved problem today, but tends to be solved right only in the better CAD systems.
(If only the HTML people had thought in terms of constraints. Left edge of box B is coincident with right edge of box A. Right edge of box B is coincident with right edge of window. Left edge of box A is coincident with left edge of window. Top edge of box A and top edge of box B are collinear. Boxes A and B have equal width. That's the way to get two columns.
Unlike CSS layout, this concept can be extended beyond rectangular boxes; constraints with circles and splines are usually solveable.)
Sketch mode in Autodesk Inventor does constraints very well, including difficult geometry problems like circles tangent to other circles. This is a solved problem today, but tends to be solved right only in the better CAD systems.
(If only the HTML people had thought in terms of constraints. Left edge of box B is coincident with right edge of box A. Right edge of box B is coincident with right edge of window. Left edge of box A is coincident with left edge of window. Top edge of box A and top edge of box B are collinear. Boxes A and B have equal width. That's the way to get two columns.
Unlike CSS layout, this concept can be extended beyond rectangular boxes; constraints with circles and splines are usually solveable.)