How does this seem to you: Adding Fractions Animation
(Also, I am not sure it is an "animation" or "demo" or what).
"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman
I would call it an animation. Great teaching aid for fractions. Excellent job!
In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.