Flexbox Overview

https://css-tricks.com/snippets/css/a-guide-to-flexbox/

flex-direction

https://css-tricks.com/almanac/properties/f/flex-direction/

justify-content

https://css-tricks.com/almanac/properties/j/justify-content/

align-items

https://css-tricks.com/almanac/properties/a/align-items/

align-content

https://css-tricks.com/almanac/properties/a/align-content/