Animation Transition for a mobile menu toggle. Three horizontal lines transform into a cross and back again. The top and bottom lines fall into the center, transforming into one line. The line(s) rotate clockwise, spawning a line at 45deg and stop at 135 deg, forming a cross. Demo: http://jsfiddle.net/SYYr5/84/
Annotations:
- the animation uses four additional elements inside the a tag. This is not semantic, but we can at least use elements without a semantic meaning, like div and span
- using a div as a second container, we are able to apply a padding to our a tag
- We may need to use vendor prefixes :/