In this example, we use Flexbox on the `.container` element to create a two-column layout.
Setting `flex: 1` on both `main` and `aside` ensures that both elements expand proportionally.
Applying `min-width` to `main` and `aside` ensures that they maintain an adequate minimum width.
The `@media` query switches the layout to a single column on devices with a maximum screen width of 768px.
This final division spans both columns and is positioned vertically on small screens.