If it's stupid but works, it isn't stupid.
A Complete Guide to Flexbox
https://css-tricks.com/snippets/css/a-guide-to-flexbox/
Прижать футер к низу
https://codepen.io/html5book/pen/QMLRLR
https://css-tricks.com/snippets/css/a-guide-to-flexbox/
Прижать футер к низу
https://codepen.io/html5book/pen/QMLRLR