* {
  box-sizing: border-box;
}

body {
  font-family: Arial, Helvetica, sans-serif;
}

.modal-box {
  display: none; /* Hidden by default */
  position: fixed; /* Stay in place */
  z-index: 1; /* Sit on top */
  left: 0;
  top: 0;
  width: 100%; /* Full width */
  height: 100%; /* Full height */
  overflow: auto; /* Enable scroll if needed */
  background-color: rgb(0,0,0); /* Fallback color */
  background-color: rgba(0,0,0,0.8); /* Black w/ opacity */
}

.modal-box[popup-display="false"] {
  display: none; /* Hidden by default */
}

.modal-box[popup-display="true"] {
  display: flex; /* Hidden by default */
}
/* Modal Content/Box */
.modal-content {
  margin: 5% auto; /* 15% from the top and centered */
  padding: 20px;
  border: 1px solid #888;
  width: 80%; /* Could be more or less, depending on screen size */
  height: 90%;
  overflow: auto; /* Enable scroll if needed */
  background-color: #f1f1f1; /* Fallback color */
}