justify-content
Distributes items on the main axis. The main axis follows flex-direction, so row and column swap its orientation.
Move frogs, inspect both axes, and see each declaration change a real layout.
.pond {
display: flex;
flex-direction: row;
justify-content: flex-start;
align-items: stretch;
flex-wrap: nowrap;
}justify-content → main axis; align-items → cross axis.
Put every frog in the center of its lily pad.
justify-contentDistributes items on the main axis. The main axis follows flex-direction, so row and column swap its orientation.
align-itemsAligns every item on the cross axis within its flex line.
align-contentDistributes flex lines in a multi-line container created with flex-wrap. It can affect a wrap container even when its contents currently form one line.
flexCombines grow, shrink, and basis on each flex item.