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. Visit 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