Code for Youtube video embed width

I have a guided landing page with a video section:

<meta class="mktoBoolean" id="videoSection" mktoName="Video" default="false" false_value="none" true_value="block" false_value_name="Hide" true_value_name="Show">

For my CSS in the videosection I have:

.videoSection

      {

        display:${videoSection};

        text-align: center;

        max-width: 100%;

      }

The video is not responsive, so I'm missing some code somewhere... I tried to look, but Product Docs are offline at the moment...

Thanks!~