如何反转CSS :checked实现侧边栏默认展开点击关闭？

核心修改逻辑：

• 调整菜单容器初始状态：将.menu__box的默认位置从left: -100%改为left: 0，让菜单默认展开
• 反转:checked触发的菜单行为：把#menu__toggle:checked ~ .menu__box的left从0改为-100%，实现选中时关闭菜单
• 反转汉堡按钮样式逻辑：将原选中状态的叉形样式设为默认样式，选中时恢复三条杠样式

修改后的完整代码：

CSS #

#menu__toggle {
  opacity: 0;
}
/* 默认按钮显示叉形（原选中状态样式） */
.menu__btn > span {
  transform: rotate(45deg);
}
.menu__btn > span::before {
  top: 0;
  transform: rotate(0deg);
}
.menu__btn > span::after {
  top: 0;
  transform: rotate(90deg);
}
/* 选中时按钮恢复三条杠 */
#menu__toggle:checked + .menu__btn > span {
  transform: rotate(0deg);
}
#menu__toggle:checked + .menu__btn > span::before {
  top: -8px;
  transform: rotate(0deg);
}
#menu__toggle:checked + .menu__btn > span::after {
  top: 8px;
  transform: rotate(0deg);
}
/* 选中时隐藏菜单 */
#menu__toggle:checked ~ .menu__box {
  left: -100% !important;
}
.menu__btn {
  position: fixed;
  top: 20px;
  left: 20px;
  width: 26px;
  height: 26px;
  cursor: pointer;
  z-index: 1;
}
.menu__btn > span,
.menu__btn > span::before,
.menu__btn > span::after {
  display: block;
  position: absolute;
  width: 100%;
  height: 2px;
  background-color: #616161;
  transition-duration: .25s;
}
.menu__btn > span::before {
  content: '';
}
.menu__btn > span::after {
  content: '';
}
.menu__box {
  display: block;
  position: fixed;
  top: 0;
  left: 0; /* 默认展开 */
  width: 300px;
  height: 100%;
  margin: 0;
  padding: 80px 0;
  list-style: none;
  background-color: #ECEFF1;
  box-shadow: 2px 2px 6px rgba(0, 0, 0, .4);
  transition-duration: .25s;
}
.menu__item {
  display: block;
  padding: 12px 24px;
  color: #333;
  font-family: 'Roboto', sans-serif;
  font-size: 20px;
  font-weight: 600;
  text-decoration: none;
  transition-duration: .25s;
}
.menu__item:hover {
  background-color: #CFD8DC;
}

HTML #

<div class="hamburger-menu">
    <input id="menu__toggle" type="checkbox" />
    <label class="menu__btn" for="menu__toggle">
      <span></span>
    </label>

    <ul class="menu__box">
      <li><a class="menu__item" href="#">Home</a></li>
            <li><a class="menu__item" href="#">About</a></li>
            <li><a class="menu__item" href="#">Team</a></li>
            <li><a class="menu__item" href="#">Contact</a></li>
            <li><a class="menu__item" href="#">Twitter</a></li>
    </ul>
  </div>

内容的提问来源于stack exchange，提问作者cakebot