Use case #4
Increase z-index of an element on click
Who was born first, chicken or egg?
Nominate the chicken or the egg by clicking on it
on click of '.chicken-container'
add class '.up' to '.chicken-container'
remove class '.up' from '.egg-container'
on click of '.egg-container'
add class '.up' to '.egg-container'
remove class '.up' from .chicken-container
Use case #4 - Video tutorial