Adding a js sandbox example

Hi Amelia,

I am editing http://docs.webplatform.org/wiki/dom/MouseEvent/layerY

I want to add a link to an example.......

I have seen a tool on WPO that is similar to jsFiddle (you enter the css, markup and script and the output is displayed in an iframe), but I can’t find a link to that tool (searched for tools)....

My question is 

1. do you have a link to that tool (if you know what I am talking about).
2. I presume that I use the uri generated by that tool to add as an external link example...
3. Failing that I will use jsFiddle or something similar that you recommend.

I hope I am asking in the right place.


Regards.