flex css shorthand
flex: none | [ <'flex-grow'> <'flex-shrink'>? || <'flex-basis'> ]
.flex-item {
/* this */
flex: 1 100px;
/* is the same as */
flex-grow: 1;
flex-basis: 100px;
/* and it leaves the flex-shrink property alone, which would be */
flex-shrink: inherit; /* defaults to 1 */
}