body {
  font-family: Arial, sans-serif;
  margin: 0;
  padding: 0;
  background: #f9f9f9;
}

header {
  background: #004080;
  padding: 10px 0;
}

nav ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  justify-content: center;
}

nav ul li {
  margin: 0 15px;
}

nav ul li a {
  color: #fff;
  text-decoration: none;
  font-weight: bold;
}

nav ul li a:hover {
  text-decoration: underline;
}

main {
  padding: 20px;
}

h1 {
  text-align: center;
  margin-bottom: 30px;
}

/* Lưới sản phẩm */
.product-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 20px;
  max-width: 1100px;
  margin: 0 auto;
}

.product-card {
  background: #fff;
  border: 1px solid #ddd;
  border-radius: 8px;
  padding: 15px;
  text-align: center;
  transition: 0.3s;
}

.product-card:hover {
  box-shadow: 0 4px 12px rgba(0,0,0,0.1);
  transform: translateY(-3px);
}

.product-card img {
  max-width: 100%;
  height: 180px;
  object-fit: contain;
  margin-bottom: 10px;
}

.product-name {
  font-weight: bold;
  margin-bottom: 5px;
}

.product-price {
  color: red;
  font-size: 18px;
}

footer {
  text-align: center;
  background: #004080;
  color: #fff;
  padding: 10px 0;
  margin-top: 30px;
}
.product-detail {
  display: flex;
  flex-wrap: wrap;
  gap: 20px;
  max-width: 900px;
  margin: 0 auto;
  background: #fff;
  padding: 20px;
  border: 1px solid #ddd;
  border-radius: 10px;
}

.product-detail img {
  flex: 1 1 300px;
  max-width: 300px;
  object-fit: contain;
}

.product-detail .info {
  flex: 2 1 400px;
}

.back-link {
  display: inline-block;
  margin-top: 20px;
  color: #004080;
  text-decoration: none;
  font-weight: bold;
}

.back-link:hover {
  text-decoration: underline;
}