body {
  display: grid;
  place-items: center; /* 水平方向・垂直方向の両方を中央寄せ */
  height: 100vh;
  margin: 0;
}
.container {
  text-align: center;
  
  img {
  max-width: 1200px;
  height: auto;
}

  .youtube-wrap {
  position: relative;
  width: 100%;
  padding-bottom: 56.25%; /* 16:9比率 */
  height: 0;
  overflow: hidden;
}
.youtube-wrap iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
}