/* Global */
body {
  font-family: Arial, sans-serif;
  margin: 0;
  background-color: #f7f7f7;
  color: #333;
}

header {
  background-color: #222;
  color: white;
  padding: 1em;
  text-align: center;
}

nav a {
  margin: 0 1em;
  color: white;
  text-decoration: none;
  display: inline-block;
  font-weight: bold;
}

nav a.active {
  text-decoration: underline;
}

main {
  padding: 2em;
  max-width: 800px;
  margin: auto;
}

footer {
  text-align: center;
  padding: 1em;
  background-color: #222;
  color: white;
  margin-top: 2em;
}

.video-container {
  margin-top: 2em;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.video-wrapper {
  position: relative;
  width: 100%;
  max-width: 640px;
  padding-bottom: 75%; /* 480/640 = 0.75 */
  height: 0;
}

.video-wrapper iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  border: none;
}

.alpha {
  font-size: 0.6em;
  font-weight: normal;
  color: #ccc;
}

.notice {
  font-size: 0.9em;
  color: #a00;
  background: #ffecec;
  padding: 1em;
  border-left: 5px solid #a00;
  margin-top: 2em;
}

/* Responsive */
@media (max-width: 600px) {
  header h1 {
    font-size: 1.2em;
  }

  nav a {
    display: block;
    margin: 0.5em 0;
  }

  main {
    padding: 1em;
  }
}