CSS

W3Schools How To
https://www.w3schools.com/howto/default.asp

CSS Flexbox
https://www.w3schools.com/css/css3_flexbox.asp

A Complete Guide to Flexbox
https://css-tricks.com/snippets/css/a-guide-to-flexbox/

CSS Grid Layout Module
https://www.w3schools.com/css/css_grid.asp

A Complete Guide to Grid
https://css-tricks.com/snippets/css/complete-guide-grid/

CSS Layout – The position Property
https://www.w3schools.com/css/css_positioning.asp

Align Items in CSS using Flexbox
https://pupli.net/2017/06/14/align-items-in-css-using-flexbox/

CSS flexbox float right
https://pupli.net/2017/07/13/css-flexbox-float-right/

How to make a div 100% height of the browser window
https://pupli.net/2019/05/18/how-to-make-a-div-100-height-of-the-browser-window/

CSS Media Queries
https://www.w3schools.com/css/css3_mediaqueries.asp

Absolute Positioning Inside Relative Positioning
https://pupli.net/2019/06/14/absolute-positioning-inside-relative-positioning/

CSS Animations
https://www.w3schools.com/css/css3_animations.asp