CSS3 Ninja – Pure CSS-KeyFrame Animation Example

An infinite, alternate animation converting a shape, with initial delay,
no javascript, pure css.

– centring the shape using the top0-left0-right0-bottom0-margin_auto trick.
– sizing the share using viewport

vw: 1/100th viewport width
vh: 1/100th viewport height
vmin: 1/100th of the smallest side
vmax: 1/100th of the largest side