Simple Modal CSS

simple-modal.css

.modal, .modal-bg {
  display: none;
}

.modal-active .modal-bg {
  display: block;
  background-color: rgba(0, 0, 0, 0.7);
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: 1000;
}

.modal-active .modal {
  display: block;
  position: fixed;
  width: 100%;
  max-width: 580px;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  z-index: 1001;
  max-height: 100%;
  overflow-y: auto;
}