body {
  font-family: 'Segoe UI', sans-serif;
  margin: 0;
  background-color: #f0f4f5;
  color: #333;
  font-size: 20px; /* tăng cỡ chữ toàn trang */
}

.container {
  width: 90%;
  max-width: 1000px;
  margin: 0 auto;
}

header {
  background-color: #004d40;
  color: white;
  padding: 40px 0 20px;
  text-align: center;
}

header h1 {
  font-size: 2.6em;
}

.subtitle {
  font-weight: 300;
  margin-top: 5px;
  color: #cfd8dc;
  font-size: 1.3em;
}

nav {
  background-color: #00796b;
  padding: 15px 0;
  box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}

.nav-buttons {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: 15px;
}

nav button {
  background-color: #004d40;
  border: none;
  color: white;
  font-weight: bold;
  font-size: 20px; /* tăng cỡ chữ nút menu */
  padding: 14px 28px;
  border-radius: 6px;
  cursor: pointer;
  transition: background 0.3s;
}

nav button:hover {
  background-color: #00695c;
}

.section {
  background: white;
  padding: 30px;
  border-radius: 8px;
  margin-top: 30px;
  box-shadow: 0 2px 12px rgba(0,0,0,0.08);
  transition: opacity 0.5s ease;
  opacity: 0;
  font-size: 1.1em;
}

.fade {
  opacity: 1;
}

footer {
  background-color: #004d40;
  color: white;
  text-align: center;
  padding: 20px 0;
  margin-top: 50px;
  font-size: 14px;
}