On a webpage, there are three columns: left, middle, and right. Only the left column is set to position:fixed, while the others are normal.
When vertically scrolling, the left column should remain fixed while the other two scroll.
However, when the browser size is reduced and horizontal scrolling is necessary, all three columns should be able to scroll horizontally, not just the middle and right columns.
How can this problem be solved using pure CSS without relying on JavaScript or jQuery?