How To Add CSS3 Transition With HTML5 details/summary tag reveal?

Question

Using just CSS3, is there a way to add a nice fade-in and slide-from-left transition effect on a DETAILS/SUMMARY reveal?

For a demo of this new tag, see this demo:

https://jsfiddle.net/43m61yt0/1/

Here's the HTML for it:

<details>
  <summary>Copyright 1999-2014.</summary>
  <section>
    <p> - by Refsnes Data. All Rights Reserved.</p>
    <p>All content and graphics on this web site are the property of the company Refsnes Data.</p>
  </section>
</details>

In my case, after the summary tag, I put all other content in its own section tag so that I could style it because summary:after selector didn't seem to work. I tried using CSS3 transitions on height for the section and details tag, but it didn't help. Here's what I tried:

<style type="text/css">
DETAILS
{
 transition:height 3s ease-in;
}
</style>

Answer 1

This should fix it.

details[open] summary ~ * {
  animation: sweep .5s ease-in-out;
}

@keyframes sweep {
  0%    {opacity: 0; margin-left: -10px}
  100%  {opacity: 1; margin-left: 0px}
}

<details>
  <summary>Copyright 1999-2014.</summary>
  <p> - by Refsnes Data. All Rights Reserved.</p>
  <p>All content and graphics on this web site are the property of the company Refsnes Data.</p>
</details>

Some credit goes to Andrew for pointing this out. I adapted his answer. Here's how this works. By adding the [open] attribute on the DETAILS tag, it only fires the animation keyframe when clicked. Then, by adding SUMMARY ~ * it means "all elements after the SUMMARY tag" so that the animation applies to those, and not the SUMMARY element as well.