bigbluebutton-Github/bigbluebutton-html5/client/stylesheets/modals.css

.ReactModal__Overlay {
  -webkit-perspective: 600;
  perspective: 600;
  opacity: 0;
  overflow-x: hidden;
  overflow-y: auto;
  background-color: rgba(0, 0, 0, 0.5);
}

.ReactModal__Overlay--after-open {
  opacity: 1;
  transition: opacity calc(var(--enableAnimation) * 150ms) ease-out;
}

.ReactModal__Content {
  -webkit-transform: scale(0.5) rotateX(-30deg);
  transform: scale(0.5) rotateX(-30deg);
  width: 600px;
}

.ReactModal__Content--after-open {
  -webkit-transform: scale(1) rotateX(0deg);
  transform: scale(1) rotateX(0deg);
  transition: all calc(var(--enableAnimation) * 150ms) ease-in;
}

.ReactModal__Overlay--before-close {
  opacity: 0;
}

.ReactModal__Content--before-close {
  -webkit-transform: scale(0.5) rotateX(30deg);
  transform: scale(0.5) rotateX(30deg);
  transition: all calc(var(--enableAnimation) * 150ms) ease-in;
}

.ReactModal__Content.modal-dialog {
  border: none;
  background-color: transparent;
}

.modal-low {
  z-index: 1001;
}

.modal-medium {
  z-index: 1002;
}

.modal-high {
  z-index: 1003;
}

/* Within a same priority, hide all but first (FIFO) */
.modal-low ~ .modal-low, 
.modal-medium ~ .modal-medium, 
.modal-high ~ .modal-high {
  display: none;
}

/* Hide all low priority modals when a medium or high priority modals are displayed */
#modals-container:has(.modal-medium) .modal-low, 
#modals-container:has(.modal-high) .modal-low {
  display: none;
}

/* Hide all medium priority modals when a high priority modal is displayed */
#modals-container:has(.modal-high) .modal-medium {
  display: none;
}