I think I did something somewhat similar: http://magako.com/exercise/fractions/eng http://magako.com/exercise/fractions/eng Unlike what you want, the nodes are

I think I did something somewhat similar: http://magako.com/exercise/fractions/eng http://magako.com/exercise/fractions/eng Unlike what you want, the nodes are not graphically connected, but somehow it can change itself. As dqdo said, I used Jquery UI draggable elements to do it.