In the Quark theme we have implemented the animation engine based on the scrollReveal.js script. This script creates elements scroll animations in a very simple way.
Thanks to this script you can describe an animation using a language very similar to natural.
Description of the animation is placed in the data-scroll-reveal attribute:
<!-- These 2 lines are equivalent --> <p data-sr="enter top and move 25px"> foo </p> <p data-sr="enter from the top and then move 25px"> foo </p>
The full description of the syntax is available on the project documentation page.