.responsive-video {
  position: relative;
  padding-bottom: 56.25%; /* 16:9 */
  height: 0;
  overflow: hidden;
  max-width: 700px; /* tamaño más pequeño */
  margin: 0 auto;
}

.responsive-video video,
.responsive-video iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
}