Akismet's sign up page has been using a similar idea since their relaunch. You can see it in action if you: 1. Visit https://akismet.com/signup/ https://akisme

Akismet's sign up page has been using a similar idea since their relaunch. You can see it in action if you: 1. Visit https://akismet.com/signup/ https://akismet.com/signup/ 2. Click "Sign Up" under the Personal plan. 3. Move the "What is Akismet worth to you?" slider. They use a sprite[1] in their version, not the canvas, but the effect is similar. I'd suggest that their implementation is a little clearer than the one presented in this thread's link; moving a control and seeing a face to the right of the slider change its expression is possibly clearer than grabbing the face itself, where your mouse pointer partially hides the expression. [1]: https://akismet.com/img/ab/smiley.png https://akismet.com/img/ab/smiley.png