justify content css not working in chrome code example

Example 1: flexbox center and space between

//You have to give an automatic margin to all the items inside the flex.
.flexbox {
       display: flex;
       justify-content:  space-between;
    }
    
    .flex-item {
       margin: auto;
    }

Example 2: gap between two flex items

.upper
{
  margin:30px;
  display:flex;
  flex-direction:row;
  width:300px;
  height:80px;
  border:1px red solid;

  padding:5px; /* this */
}

.upper > div
{
  flex:1 1 auto;
  border:1px red solid;
  text-align:center;

  margin:5px;  /* and that, will result in a 10px gap */
}

.upper.mc /* multicol test */
{flex-direction:column;flex-wrap:wrap;width:200px;height:200px;}