Flexbox YouTube Thumbnail Grid

index.html

<main role="main">
  <section class="videos" id="featured-videos">
    <div class="video-grid front-page" id="front-page-videos">
      <ul class="video-list featured">
        <li class="video featured">
          <a data-fancybox href="https://www.youtube.com/embed/Zq6Crtglztk?autoplay=1&controls=0&showinfo=0&color=white&rel=0" class="featured-video">
            <figure style="background-image: url(https://img.youtube.com/vi/Zq6Crtglztk/hqdefault.jpg);">
              <img src="https://s3-us-west-2.amazonaws.com/s.cdpn.io/50598/video-thumb-placeholder-16-9.png" />
              <figcaption>Swap-Meet Speed for Roadkill Nights</figcaption>
            </figure>
          </a>
        </li>
        <li class="video featured">
          <a data-fancybox href="https://www.youtube.com/embed/qDK86kzgUPg?autoplay=1&controls=0&showinfo=0&color=white&rel=0" class="featured-video">
            <figure style="background-image: url(https://img.youtube.com/vi/qDK86kzgUPg/hqdefault.jpg);">
              <img src="https://s3-us-west-2.amazonaws.com/s.cdpn.io/50598/video-thumb-placeholder-16-9.png" />
              <figcaption>Cummins Diesel in a Cadillac</figcaption>
            </figure>
          </a>
        </li>
        <li class="video featured">
          <a data-fancybox href="https://www.youtube.com/embed/uSB2_428P2w?autoplay=1&controls=0&showinfo=0&color=white&rel=0" class="featured-video">
            <figure style="background-image: url(https://img.youtube.com/vi/uSB2_428P2w/hqdefault.jpg);">
              <img src="https://s3-us-west-2.amazonaws.com/s.cdpn.io/50598/video-thumb-placeholder-16-9.png" />
              <figcaption>Dirt-Track Challenger Rescue and Thrash</figcaption>
            </figure>
          </a>
        </li>
        <li class="video featured">
          <a data-fancybox href="https://www.youtube.com/embed/pOhl6oVpEes?autoplay=1&controls=0&showinfo=0&color=white&rel=0" class="featured-video">
            <figure style="background-image: url(https://img.youtube.com/vi/pOhl6oVpEes/hqdefault.jpg);">
              <img src="https://s3-us-west-2.amazonaws.com/s.cdpn.io/50598/video-thumb-placeholder-16-9.png" />
              <figcaption>Junkyard 1956 Buick Hack</figcaption>
            </figure>
          </a>
        </li>
        <li class="video featured">
          <a data-fancybox href="https://www.youtube.com/embed/PVs_xZ46Cxw?autoplay=1&controls=0&showinfo=0&color=white&rel=0" class="featured-video">
            <figure style="background-image: url(https://img.youtube.com/vi/PVs_xZ46Cxw/hqdefault.jpg);">
              <img src="https://s3-us-west-2.amazonaws.com/s.cdpn.io/50598/video-thumb-placeholder-16-9.png" />
              <figcaption>Wheelstanding Dump Truck! Stubby Bob’s Comeback</figcaption>
            </figure>
          </a>
        </li>
        <li class="video featured">
          <a data-fancybox href="https://www.youtube.com/embed/C4jk51rgfts?autoplay=1&controls=0&showinfo=0&color=white&rel=0" class="featured-video">
            <figure style="background-image: url(https://img.youtube.com/vi/C4jk51rgfts/hqdefault.jpg);">
              <img src="https://s3-us-west-2.amazonaws.com/s.cdpn.io/50598/video-thumb-placeholder-16-9.png" />
              <figcaption>Will It Go 10s? Mazdarati Is Back!</figcaption>
            </figure>
          </a>
        </li>
      </ul>
    </div
  </section>
</main>

scripts

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<script src="https://s3-us-west-2.amazonaws.com/s.cdpn.io/50598/jquery.fancybox-three.min.js"></script>

style.scss

/**
 * Grid styles
 */
.video-grid.front-page {
  max-width: 1280px;
  margin: 0 auto;
  padding: 1em 2em;
}

ul.video-list {
  display: flexbox;
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
}

li.video {
  flex-grow: 1;
  position: relative;
  ooverflow: hidden;
  width: 33.333333333%;
  width: -webkit-calc(100% / 3);
  width: calc(100% / 3);
  border: solid 0.2em transparent;

  & a {
    outline: none;
  }

  &:before {
    content: "";
    display: block;
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0);
    transition: background-color 0.15s;
  }

  & figure {
    display: block;
    position: relative;
    overflow: hidden;
    background-repeat: no-repeat;
    background-position: center center;
    background-size: cover;

    & img {
      display: block;
      max-width: 100%;
      height: auto;
      opacity: 0;
      transform: scale(0.5);
      transition: all 0.2s;
    }

    & figcaption {
      position: absolute;
      bottom: 0;
      width: 100%;
      background: rgba(0, 0, 0, 0.6);
      color: #fff;
      font-size: 1.4rem;
      font-weight: 600;
      padding: 1rem;
      transform: translateY(0);
      opacity: 1;
      transition: all 0.2s;
    }
  }

  &:hover {
    & figure {
      & img {
        opacity: 1;
        transform: scale(1);
      }

      & figcaption {
        opacity: 0;
        transform: translateY(50%);
      }
    }
  }

  &:hover:before {
    background-color: rgba(0, 0, 0, 0.3);
  }
}

@media screen and (max-width: 800px) {
  li.video {
    width: 50%;
    width: -webkit-calc(100% / 2);
    width: calc(100% / 2);
  }
}

@media screen and (max-width: 640px) {
  li.video {
    width: 100%;
  }
}

/**
 * Pen styles
 */
html {
  box-sizing: border-box;
  height: 100%;
  overflow-y: scroll;
  font-size: 62.5%;
}
*,
*:before,
*:after {
  box-sizing: inherit;
}
body {
  background: #fff;
  color: #444;
  font-family: "Open Sans", Arial, -apple-system, BlinkMacSystemFont, "Segoe UI",
    Roboto, Oxygen-Sans, Ubuntu, Cantarell, "Helvetica Neue", sans-serif;
  font-size: 1.8rem;
  line-height: 1.2;
}


main {
  padding: 2rem 0;
}

article {
  max-width: 1280px;
  margin: 0 auto;
  padding: 1em 2em;
}

styles

<link href="https://s3-us-west-2.amazonaws.com/s.cdpn.io/50598/jquery.fancybox-three.min.css" rel="stylesheet" />