https://codepen.io/mycenas/pen/NWJodRE I have created 4 rows of 3 boxes with flex, and on click a flex-grow property is applied. No matter how much I increase the number, the boxes will only expand a small amount. I want the clicked box to expand to take up approx 2/3rds of the row, and the other 3 boxes on the row shrink to accommodate it.