.mask {
  position: fixed;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  width: 100%;
  height: 100%;
  overflow: auto;
  z-index: 1;
  box-sizing: border-box;
  background-color: rgba(0, 0, 0, 0.75);
  text-align: center;
}
.mask:before {
  content: "";
  display: inline-block;
  height: 100%;
  vertical-align: middle;
}
.modal {
  display: none;
  vertical-align: middle;
  position: relative;
  z-index: 2;
  max-width: 540px;
  width: 90%;
  box-sizing: border-box;
  background: #fff;
  padding: 15px 30px;
  border-radius: 8px;
  box-shadow: 0 0 10px #000;
  text-align: left;
}

.modal a.close-modal {
  position: absolute;
  top: 10px;
  right: 10px;
  display: block;
  width: 16px;
  height: 16px;
  text-indent: -9999px;
  background-size: contain;
  background-repeat: no-repeat;
  background-position: center center;
  background-image: url(data:image/png;base64,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);
}