<!DOCTYPE html> <!-- Any copyright is dedicated to the Public Domain. http://creativecommons.org/publicdomain/zero/1.0/ --> <!-- Reference case, with testcase's dynamic tweak already performed. --> <html> <head> <style> div#outer { margin-left: 40px } div#flexContainer { width: 100px; height: 50px; background: lightgray; display: flex; justify-content: center; } div#flexItem { border: 1px solid black; height: 200%; background: purple; } </style> </head> <body> <div id="outer"> <div id="flexContainer"> <div id="flexItem">item</div> </div> </div> </body> </html>