* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: 'Segoe UI', sans-serif;
}

body {
  background: linear-gradient(to bottom right, #f0f2f5, #dce3ec);
  color: #333;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

header {
  background: linear-gradient(to right, #6a85b6, #bac8e0);
  padding: 20px;
  text-align: center;
  color: #fff;
  box-shadow: 0 2px 6px rgba(0, 0, 0, 0.15);
}

header h1 {
  font-size: 2em;
  margin-bottom: 10px;
}

nav ul {
  list-style: none;
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: 20px;
}

nav ul li a {
  text-decoration: none;
  color: #fff;
  font-weight: bold;
  padding: 10px 16px;
  background-color: rgba(255, 255, 255, 0.2);
  border-radius: 8px;
  transition: background-color 0.3s ease;
}

nav ul li a:hover {
  background-color: rgba(255, 255, 255, 0.35);
}

main {
  flex: 1;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 50px 20px;
}

main section {
  background-color: #ffffffcc;
  padding: 30px;
  border-radius: 16px;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.12);
  text-align: center;
}

main h2 {
  font-size: 1.8em;
  margin-bottom: 15px;
  color: #2c3e50;
}

footer {
  background: #c9d6e3;
  padding: 15px;
  text-align: center;
  font-size: 0.9em;
  color: #555;
  border-top: 1px solid #aaa;
}
/* Dành cho màn hình nhỏ <= 600px (điện thoại) */
@media only screen and (max-width: 600px) {
   header h1 {
    font-size: 1.4em;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis; /* Nếu quá dài thì hiển thị dấu ... */
  }
  nav ul {
    flex-direction: column;
    padding: 50;
  }

  nav ul li {
    margin-bottom: 15px; /* khoảng cách giữa các item */
  }

  nav ul li:last-child {
    margin-bottom: 0; /* bỏ margin dưới cùng để không dư */
  }

  nav ul li a {
    padding: 8px 12px;
    font-size: 0.9em;
  }
  
}