This is cool man. I use an MBPR and never knew how to get back down to 1x resolutions. Just saved me a couple of steps in my workflow. Wasn't sure how useful the animations were going to be, but turns out very much so. Solid tool; much obliged.
To my knowledge this is incorrect. Assistive technologies don't recognize input names when nested inside of label elements, and as a result is frowned upon by the W3C. Unless you meant something else by, "...HTML has always allowed nesting an <input> inside <label>..."