use https://github.com/nunocoracao/blowfish.git

themes/blowfish/assets/lib/lite-youtube-embed/lite-yt-embed.css

@@ -0,0 +1,95 @@
+lite-youtube {
+    background-color: #000;
+    position: relative;
+    display: block;
+    contain: content;
+    background-position: center center;
+    background-size: cover;
+    cursor: pointer;
+    max-width: 720px;
+}
+
+/* gradient */
+lite-youtube::before {
+    content: attr(data-title);
+    display: block;
+    position: absolute;
+    top: 0;
+    /* Pixel-perfect port of YT's gradient PNG, using https://github.com/bluesmoon/pngtocss plus optimizations */
+    background-image: linear-gradient(180deg, rgb(0 0 0 / 67%) 0%, rgb(0 0 0 / 54%) 14%, rgb(0 0 0 / 15%) 54%, rgb(0 0 0 / 5%) 72%, rgb(0 0 0 / 0%) 94%);
+    height: 99px;
+    width: 100%;
+    font-family: "YouTube Noto",Roboto,Arial,Helvetica,sans-serif;
+    color: hsl(0deg 0% 93.33%);
+    text-shadow: 0 0 2px rgba(0,0,0,.5);
+    font-size: 18px;
+    padding: 25px 20px;
+    overflow: hidden;
+    white-space: nowrap;
+    text-overflow: ellipsis;
+    box-sizing: border-box;
+}
+
+lite-youtube:hover::before {
+    color: white;
+}
+
+/* responsive iframe with a 16:9 aspect ratio
+    thanks https://css-tricks.com/responsive-iframes/
+*/
+lite-youtube::after {
+    content: "";
+    display: block;
+    padding-bottom: calc(100% / (16 / 9));
+}
+lite-youtube > iframe {
+    width: 100%;
+    height: 100%;
+    position: absolute;
+    top: 0;
+    left: 0;
+    border: 0;
+}
+
+/* play button */
+lite-youtube > .lty-playbtn {
+    display: block;
+    /* Make the button element cover the whole area for a large hover/click target… */
+    width: 100%;
+    height: 100%;
+    /* …but visually it's still the same size */
+    background: no-repeat center/68px 48px;
+    /* YT's actual play button svg */
+    background-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 68 48"><path d="M66.52 7.74c-.78-2.93-2.49-5.41-5.42-6.19C55.79.13 34 0 34 0S12.21.13 6.9 1.55c-2.93.78-4.63 3.26-5.42 6.19C.06 13.05 0 24 0 24s.06 10.95 1.48 16.26c.78 2.93 2.49 5.41 5.42 6.19C12.21 47.87 34 48 34 48s21.79-.13 27.1-1.55c2.93-.78 4.64-3.26 5.42-6.19C67.94 34.95 68 24 68 24s-.06-10.95-1.48-16.26z" fill="red"/><path d="M45 24 27 14v20" fill="white"/></svg>');
+    position: absolute;
+    cursor: pointer;
+    z-index: 1;
+    filter: grayscale(100%);
+    transition: filter .1s cubic-bezier(0, 0, 0.2, 1);
+    border: 0;
+}
+
+lite-youtube:hover > .lty-playbtn,
+lite-youtube .lty-playbtn:focus {
+    filter: none;
+}
+
+/* Post-click styles */
+lite-youtube.lyt-activated {
+    cursor: unset;
+}
+lite-youtube.lyt-activated::before,
+lite-youtube.lyt-activated > .lty-playbtn {
+    opacity: 0;
+    pointer-events: none;
+}
+
+.lyt-visually-hidden {
+    clip: rect(0 0 0 0);
+    clip-path: inset(50%);
+    height: 1px;
+    overflow: hidden;
+    position: absolute;
+    white-space: nowrap;
+    width: 1px;
+  }