/* 頂部導覽列 */
.top-nav {
  position: fixed;
  top: -70px; /* 初始隱藏 */
  left: 0;
  right: 0;
  height: 70px;
  background: #666464;
  color: #fff;
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0 20px;
  transition: top 0.3s ease;
  z-index: 1000;
}

.top-nav.show {
  top: 0; /* 顯示 */
}

.logo {
  font-size: 20px;
  font-weight: bold;
}

.menu ul {
  display: flex;
  list-style: none;
  margin: 0;
  padding: 0;
}

.menu ul li {
  margin-left: 20px;
}

.menu ul li a {
  color: #fff;
  text-decoration: none;
}

/* 漢堡按鈕 */
.menu-toggle {
  display: none;
  font-size: 24px;
  background: none;
  border: none;
  color: #fff;
  cursor: pointer;
}

/* 手機版 */
@media (max-width: 768px) {
  .menu ul {
    flex-direction: column;
    display: none;
    background: #666464;
    position: absolute;
    top: 70px;
    right: 0;
    width: 200px;
  }

  .menu ul li {
    margin: 10px;
  }

  .menu-toggle {
    display: block;
  }

  .menu.active ul {
    display: flex;
  }
}

/* 回到最上面按鈕 */
#backToTop {
  position: fixed;
  bottom: 20px;
  right: 20px;
  display: none;
  background: #666464;
  color: #fff;
  border: none;
  padding: 10px 15px;
  cursor: pointer;
  border-radius: 5px;
}