* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: Arial, sans-serif;
  background: #f4f4f4;
  color: #333;
  line-height: 1.6;
  transition: background 0.3s ease;
}

header {
  background: #0077ff;
  color: white;
  text-align: center;
  padding: 60px 20px;
}

header button {
  margin-top: 20px;
  padding: 10px 18px;
  border: none;
  background: white;
  color: #0077ff;
  font-size: 16px;
  cursor: pointer;
  border-radius: 6px;
}

main {
  max-width: 900px;
  margin: 30px auto;
  padding: 0 20px;
}

.card {
  background: white;
  padding: 25px;
  margin-bottom: 20px;
  border-radius: 10px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.1);
}

.card h2 {
  margin-bottom: 10px;
}

footer {
  text-align: center;
  padding: 20px;
  background: #222;
  color: white;
  margin-top: 40px;
}

.dark {
  background: #121212;
  color: white;
}

.dark .card {
  background: #1f1f1f;
}