Create a diagonal background effect with transform property skew

Discover the CSS transform property value named "skew" to create diagonal background effects.

We will also see how to animate a button background to do a filling animation with this same diagonal effect.

The final codepen
https://codepen.io/wass08/pen/XWYMNZW

The transform property
https://www.w3schools.com/cssreF/css3_pr_transform.php