body {
  background: url(http://static.pexels.com/wp-content/uploads/2014/07/darkness-dawn-dusk-2073.jpg) no-repeat;
  background-size: 1920px 1000px;
}
.show {
  position: absolute;
  top: 50%;
  left: 50%;
  width: 150px;
  height: 40px;
  margin-top: -20px;
  margin-left: -75px;
  background: #e74c3c;
  color: #fff;
  border-radius: 5px;
  border: 0;
  border-bottom: 2px solid #c0392b;
  cursor: pointer;
}
.show:hover {
  background: #c0392b;
}
.show:active {
  transform: scale(0.9);
}
.close {
  position: absolute;
  top: 0;
  right: 0;
  width: 35px;
  height: 30px;
  background: #000;
  color: #fff;
  cursor: pointer;
  border: 0;
}
.mask {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(52, 73, 94, 0.8);
  z-index: 50;
  visibility: hidden;
  opacity: 0;
  transition: 0.7s;
}
.modal {
  position: fixed;
  top: 50%;
  left: 50%;
  width: 400px;
  height: 300px;
  margin-left: -200px;
  margin-top: -150px;
  background: #bdc3c7;
  z-index: 100;
  visibility: hidden;
  opacity: 0;
  transition: 0.5s ease-out;
  transform: translateY(45px);
}
.active {
  visibility: visible;
  opacity: 1;
}
.active + .modal {
  visibility: visible;
  opacity: 1;
  transform: translateY(0);
}