title: Creating a circular mouseover saturation effect
body: <p>I have two versions of an image: a desaturated version and a full color version. What I want to accomplish is a hover effect in which mousing over the desaturated image reveals a circle of the color version of the image. It would be sort of like shining a spotlight on the desaturated image to show its color. And then when you move the mouse away, it would fade back to its desaturated state.</p>
  
  <p>I know I could probably use flash, but I'd like to do this with JavaScript and CSS. Ideally this would degrade to just an image if JavaScript is disabled and could be fluid in width (responsive).</p>