body {
  margin: 0;
  padding: 0;
  font-family: 'Segoe UI', sans-serif;
  background: #121212;
  color: white;
  overflow-x: hidden;
}

.background-overlay {
  position: fixed;
  width: 100%;
  height: 100%;
  background-image: url('assets/bg.png'); /* hoặc ảnh bạn chọn làm nền */
  background-size: cover;
  background-position: center;
  opacity: 0.2;
  z-index: -1;
}

header {
  text-align: center;
  padding-top: 60px;
}

.logo {
  width: 320px;
  max-width: 90%;
}

.subtitle {
  margin-top: 10px;
  color: #ccc;
  font-size: 1.2em;
}

.selection {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: 40px;
  margin: 60px auto;
  padding: 20px;
}

.card {
  width: 240px;
  height: 320px;
  background: white;
  color: black;
  border-radius: 12px;
  text-decoration: none;
  text-align: center;
  padding: 30px 20px;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
  box-shadow: 0 4px 10px rgba(0,0,0,0.3);
}

.card:hover {
  transform: scale(1.05);
  box-shadow: 0 6px 20px rgba(0,0,0,0.4);
}

.orange-card {
  background: linear-gradient(135deg, #ff9800, #ff6d00);
  color: white;
}

.blue-card {
  background: linear-gradient(135deg, #03a9f4, #0288d1);
  color: white;
}

.red-card {
  background: linear-gradient(135deg, #e53935, #b71c1c); /* đỏ tươi -> đỏ đậm */
  color: white;
}

.blue-card {
  background: linear-gradient(135deg, #006064, #004d40); /* xanh nước biển than */
  color: white;
}



.card h2 {
  font-size: 1.5em;
  margin-bottom: 10px;
}

.card p {
  font-size: 1em;
}