body {
    font-family: sans-serif;
    line-height: 1.6;
    margin: 0;
    padding: 0;
    background: #f9f9f9;
}
header, footer {
    background: #004466;
    color: white;
    text-align: center;
    padding: 1rem;
}
section {
    padding: 2rem;
    max-width: 800px;
    margin: auto;
    background: white;
    margin-top: 1rem;
    border-radius: 8px;
}
h1, h2 {
    color: #004466;
}
ul {
    padding-left: 1.2rem;
}
form {
    display: flex;
    flex-direction: column;
}
input, textarea {
    margin-bottom: 1rem;
    padding: 0.8rem;
    font-size: 1rem;
}
button {
    padding: 0.8rem;
    font-size: 1rem;
    background: #004466;
    color: white;
    border: none;
    cursor: pointer;
}


/* Responsive layout cho mobile */
@media (max-width: 768px) {
    header, footer {
        padding: 1rem 0.5rem;
    }
    section {
        padding: 1rem;
        margin: 1rem;
    }
    h1 {
        font-size: 1.5rem;
    }
    h2 {
        font-size: 1.2rem;
    }
    img {
        max-width: 100%;
        height: auto;
    }
    form input, form textarea, form button {
        width: 100%;
        box-sizing: border-box;
    }
}
/* === Header Navigation === */
.nav-link {
  color: #fff;
  text-decoration: none;
  font-weight: 500;
}

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

/* Responsive menu */
@media (max-width: 768px) {
  #main-nav ul {
    flex-direction: column;
    gap: 10px;
    margin-top: 10px;
  }

  #main-nav {
    display: none;
    width: 100%;
  }

  #main-nav.show {
    display: block;
  }

  #menu-toggle {
    display: block;
    margin-bottom: 10px;
  }
}
/* Footer link style */
.footer-link {
    color: #dddddd;
    text-decoration: none;
    font-weight: 400;
}

.footer-link:hover {
    text-decoration: underline;
    color: #ffffff;
}