body {
  font-family: Arial, sans-serif;
  background-color: #f0f8ff;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

header {
  z-index: 5;
  position: sticky;
  top:0;
  background-color: #000000ba;
  color: white;
  padding: 15px 20px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.menu {
  display: flex;
  gap: 20px;
}

.menu-link {
  color: white;
  text-decoration: none;
  padding: 8px 16px;
  border-radius: 20px;
  transition: 0.3s;
}

.menu-link:hover {
  background-color: white;
  color: black;
}

main {
  flex: 1;
  padding: 30px;
  text-align: center;
}

.contact-form {
  display: flex;
  flex-direction: column;
  max-width: 400px;
  margin: 0 auto;
  gap: 15px;
}

.contact-form input,
.contact-form textarea {
  padding: 10px;
  border-radius: 8px;
  border: 1px solid #ccc;
}

.contact-form button {
  padding: 10px;
  border: none;
  border-radius: 8px;
  background-color: #2196f3;
  color: white;
  font-weight: bold;
  cursor: pointer;
}

.contact-form button:hover {
  background-color: #1976d2;
}

footer {
  background-color: #000000ba;
  color: white;
  padding: 15px;
  text-align: center;
}
.logout-btn {
  display: inline-block;
  padding: 6px 12px;
  background-color: #ff4d4d;
  color: white;
  text-decoration: none;
  border-radius: 6px;
  font-weight: bold;
  transition: background-color 0.3s ease;
  margin-left: 10px;
}

.logout-btn:hover {
  background-color: #e60000;
}

@media only screen and (max-width: 600px) {
  header {
    position: static !important; /* bỏ sticky trên điện thoại */
    flex-direction: column;
    align-items: flex-start;
    padding: 10px 15px;
    gap: 10px;
  }

  .menu {
    flex-direction: column;
    gap: 12px;
    width: 100%;
  }

  .menu-link {
    display: block;
    width: 100%;
    padding: 12px 15px;
    font-size: 1em;
    box-sizing: border-box;
  }

  main {
    padding: 20px 10px;
  }

  .contact-form {
    max-width: 100%;
    padding: 0 10px;
    gap: 12px;
  }

  .contact-form input,
  .contact-form textarea,
  .contact-form button {
    width: 100%;
    box-sizing: border-box;
  }

  footer {
    padding: 15px 10px;
    font-size: 0.9em;
  }
}