Simplicity! I&#x27;m in love. Thanks.<p>Actually, your simple design is not the only one to make my day. I have finally found a guy who puts all the HTML5 etc. on the one page. He&#x27;s a physics lecturer. He has dead easy html files that illustrate Newton&#x27;s Cannon, using canvas and javascript. Finally, I am &quot;getting&quot; it. See <a href="http:&#x2F;&#x2F;physics.weber.edu&#x2F;schroeder&#x2F;html5&#x2F;" rel="nofollow">http:&#x2F;&#x2F;physics.weber.edu&#x2F;schroeder&#x2F;html5&#x2F;</a>. (And the bonus was to see that, with uniform circular motion, the acceleration is towards the centre of rotation. I mean I really need things explained simply without any extras getting in the way.) Of course, I had to play with it to understand it. But the beauty was that, with the source code all there on the one page, I could easily make changes and see the effect immediately. Thanks Dan Schroeder.<p>PS I need to remind myself that posting pdf files is another straightforward way to get information online.