html,
body {
  width: 100%;
  height: 100%;
  margin: 0 auto;
  color: #222;
  -webkit-text-size-adjust: none;
  -webkit-font-smoothing: antialiased;
}

body,
.panel {
  background-color: #fff;
}

a {
  color: #4B5;
  text-decoration: none;
}

.panel {
  text-align: center;
  padding-top: 5px;
  min-height: 100%;
}

/* 侧边栏菜单 - 覆盖模式 */
.menu {
  position: fixed;
  left: -290px;
  top: 0;
  bottom: 0;
  width: 290px;
  z-index: 1000;
  background-color: rgba(237, 237, 237, 0.4);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
  transition: left 0.25s ease;
  box-shadow: 2px 0 20px rgba(0,0,0,0.15);
}

.menu.open {
  left: 0;
}

/* 遮罩层 */
.menu-overlay {
  position: fixed;
  inset: 0;
  z-index: 999;
  background: rgba(0, 0, 0, 0.35);
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.25s ease, visibility 0.25s ease;
}
.menu-overlay.show {
  opacity: 1;
  visibility: visible;
}

/* 侧边栏按钮 */
.btn-hamburger {
  cursor: pointer;
  width: 40px;
  height: 40px;
  border: none;
  position: absolute;
  top: 15px;
  left: 10px;
  outline: none;
  z-index: 10;
}

.btn-hamburger img {
  width: 40px;
  height: 40px;
}

@media all and (min-width: 40em) {
  .btn-hamburger {
    top: 20px;
    left: 30px;
  }
}

/* 侧边栏打开时禁止body滚动 */
.menu-open,
.menu-open body {
  overflow: hidden;
}