body {
  font-family: 'Segoe UI', Arial, sans-serif;
  background: #f7f8fa;
  color: #222;
  margin: 0;
  padding: 0;
}
header {
  text-align: center;
  padding: 2rem 1rem 1rem 1rem;
}
.intro {
  font-size: 1.2rem;
  margin: 1rem 0 2rem 0;
}
.coupon-section {
  display: flex;
  flex-direction: column;
  align-items: center;
  margin: 2rem 0;
}
.coupon-btn {
  font-size: 2.5rem;
  font-weight: bold;
  background: #2176ff;
  color: #fff;
  border: none;
  border-radius: 12px;
  padding: 1rem 3rem;
  cursor: pointer;
  box-shadow: 0 2px 8px rgba(0,0,0,0.08);
  transition: background 0.2s;
}
.coupon-btn:hover {
  background: #1856b6;
}
.coupon-desc {
  margin-top: 1rem;
  color: #555;
}
main {
  max-width: 600px;
  margin: 0 auto;
  padding: 0 1rem;
}
h2 {
  margin-top: 2rem;
  color: #2a7ae2;
}
footer {
  text-align: center;
  padding: 2rem 1rem 1rem 1rem;
  font-size: 0.95rem;
  color: #888;
}
footer nav a {
  color: #2a7ae2;
  text-decoration: none;
  margin: 0 0.5rem;
}
footer nav a:hover {
  text-decoration: underline;
}
.site-logo {
  width: 420px;
  height: 160px;
  max-width: 100%;
  display: block;
  margin: 0 auto;
}

@media (prefers-color-scheme: dark) {
  body {
    background: #181a1b;
    color: #f1f3f6;
  }
  header, footer {
    background: #23272a;
    color: #bfc9d1;
  }
  .coupon-btn {
    background: #2176ff;
    color: #fff;
  }
  .coupon-btn:hover {
    background: #1856b6;
  }
  .coupon-desc {
    color: #bfc9d1;
  }
  h2 {
    color: #6cb6ff;
  }
  footer nav a {
    color: #6cb6ff;
  }
}

@media (max-width: 600px) {
  header {
    padding: 1.2rem 0.5rem 0.5rem 0.5rem;
  }
  .site-logo {
    width: 90vw;
    height: auto;
    max-width: 95vw;
  }
  .intro {
    font-size: 1rem;
    margin: 0.7rem 0 1.2rem 0;
  }
  .coupon-btn {
    font-size: 1.5rem;
    padding: 0.8rem 1.2rem;
    border-radius: 10px;
  }
  main {
    padding: 0 0.5rem;
  }
  article, section {
    padding: 0;
  }
  h1 {
    font-size: 1.5rem;
  }
  h2 {
    font-size: 1.1rem;
    margin-top: 1.2rem;
  }
  h3 {
    font-size: 1rem;
  }
  ul, ol {
    padding-left: 1.2rem;
  }
  footer {
    padding: 1.2rem 0.5rem 0.5rem 0.5rem;
    font-size: 0.9rem;
  }
}

@media (max-width: 400px) {
  .coupon-btn {
    font-size: 1.1rem;
    padding: 0.6rem 0.7rem;
  }
  h1 {
    font-size: 1.1rem;
  }
  h2 {
    font-size: 1rem;
  }
}