http://www.flexboxdefense.com/
https://flexboxfroggy.com/
http://flexboxzombies.com/
http://the-echoplex.net/flexyboxes/
https://demos.scotch.io/visual-guide-to-css3-flexbox-flexbox-playground/demos/
By Hamza Erbay
Intended design in there https://dribbble.com/shots/3265678-Flexbox