You wouldn't want to use a single `margin: auto`, because that sets the top and bottom margins to `auto` as well. For example if the parent container is flex, y

You wouldn't want to use a single `margin: auto`, because that sets the top and bottom margins to `auto` as well. For example if the parent container is flex, you'd then end up with a container that is centered vertically as well, which is not what you wanted. What you're probably looking for is `margin: 0 auto`.