.mask {
  position: fixed;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
  background: rgba(0, 0, 0, 0.3);
  z-index: 2;
}

.mask .inner {
  display: inline-block;
  padding: 20px 15px;
  background-color: white;
  border-width: 1px;
  border-color: white;
  border-radius: 2px;
  -moz-box-shadow: 0px 1px 5px rgba(153, 153, 153, 0.34902);
  -webkit-box-shadow: 0px 1px 5px rgba(153, 153, 153, 0.34902);
  box-shadow: 0px 1px 5px rgba(153, 153, 153, 0.34902);
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  z-index: 3;
}