A neat little trick
You can achieve what you want by using a trick to check if the <section>
element is the only element in <main>
. This will not work, if there are any other elements there. In your case it should work like this (http://jsfiddle.net/Ljm323qb/2/):
section {
max-width: 500px;
}
/* The STAR of the show */
section:only-child {
max-width: 1000px;
}
As illustrated in this codepen: http://codepen.io/omarjuvera/pen/ByXGyK?editors=110
General stuff on Sibling Selectors
There’s the +
selector which would select a sibling that comes right after the element (https://developer.mozilla.org/en-US/docs/Web/CSS/Adjacent_sibling_selectors)
And there’s the ~
selector which selects all following siblings (https://developer.mozilla.org/en-US/docs/Web/CSS/General_sibling_selectors)
You could achieve it by putting the <aside>
element before the <section>
element and using a sibling selector.
Here’s an example: http://jsfiddle.net/Ljm323qb/1/
A quick look in the future
Soon this will be possible, with a new :has
pseudo class (http://dev.w3.org/csswg/selectors-4/#relational)
You’ll be able to call something like main:has(> aside) > section { ... }
but we’ll have to wait for that, unfortunately 🙁