body {
  font-family: Arial, sans-serif;
  background-color: #121212;
  color: #e0e0e0;
  margin: 0;
  padding: 0;
}
main {
  max-width: 800px;
  margin: 0 auto;
  padding: 20px;
  background: #1e1e1e;
  box-shadow: 0 0 10px rgba(255,255,255,0.05);
}
h1 {
  color: #00bcd4;
  text-align: center;
}
.subtitle {
  font-style: italic;
  color: #80cbc4;
  text-align: center;
}
ul, ol {
  margin-left: 20px;
}
footer {
  margin-top: 40px;
  text-align: center;
  font-size: 0.9em;
  color: #aaa;
}
a {
  color: #64b5f6;
}
a:hover {
  text-decoration: underline;
}
.qr {
  width: 150px;
  margin-top: 10px;
}
@media (max-width: 600px) {
  body {
    padding: 10px;
  }
  main {
    padding: 15px;
  }
  .qr {
    width: 100px;
  }
}