* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Segoe UI", "Noto Sans JP", sans-serif;
  background: #f4f6f8;
  color: #333;
  overflow-y: hidden;
  line-height: 1.6;
}

header {
  position: sticky;
  z-index: 1000;

  background: #1f2937;
  color: #fff;
  padding: 15px 23px;
  font-size: 20px;
  font-weight: bold;
}

header a {
  text-decoration: none; /* 下線を消す */
  color: inherit;        /* 親要素の色を使う */
}

a:visited,
a:hover,
a:active {
  text-decoration: none;
  color: inherit;
}

.container {
  max-width: 800px;
  margin: 0 auto;
  background: #fff;
  padding: 24px;
  border-radius: 12px;
  box-shadow: 0 8px 24px rgba(0,0,0,0.08);
}

h1 {
  font-size: 1.8rem;
  margin-bottom: 16px;
}

p {
  margin-bottom: 16px;
}

video {
  width: 100%;
  border-radius: 8px;
  background: #000;
}

.note {
  margin-top: 16px;
  font-size: 0.9rem;
  color: #555;
}

footer {
  text-align: center;
  padding: 16px;
  color: #777;
  font-size: 12px;
}