Example: ```scss div.mobile.event.container { display: flex; justify-content: center; align-items: center; div.column { .arrow { // percentage height in flex with dynamic main size doesn't work height: 80%; } } } ``` Reference: - https://stackoverflow.com/questions/29049715/how-to-control-child-div-height-of-a-flex-item - https://stackoverflow.com/questions/33502702/flex-elements-ignore-percent-padding-in-firefox - https://www.w3.org/TR/css-flexbox-1/#change-201403-definite-flexing