css make a cell twice as big flexbox

1.container {
2  display: grid;
3  grid-template-columns: 1fr 1fr;
4  grid-gap: 10px;
5}
6
7.child.featured {
8  grid-row-end: span 2;
9}
10
11
12/* non-essential decorative styles */
13.container {
14  padding: 10px;
15  border: 2px solid gray;
16  background-color: lightgray;
17  height: 50vh;
18}
19.child {
20  background-color: deepskyblue;
21  display: flex;
22  align-items: center;
23  justify-content: center;
24  font-size: 1.3em;
25}