.mask {
  box-sizing: border-box;
  position: fixed;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  z-index: 1040;
  opacity: 0;
  width: 100vw;
  height: 100vh;
  background-color: #000;
  transition: opacity 0.15s linear;
}

.mask.show {
  opacity: 0.5;
}

.mask.hide {
  opacity: 0;
}