discourse/app/assets/stylesheets/common/base/dialog.scss

.dialog-container,
.dialog-overlay {
  position: fixed;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
}

.dialog-container {
  z-index: z("modal", "dialog");
  display: flex;
}

/**
 * Ensures the dialog container and all its descendants are not
 * visible and not focusable when it is hidden.
 */
.dialog-container[aria-hidden="true"] {
  display: none;
}

@keyframes fade-in {
  from {
    opacity: 0;
  }
}

.dialog-overlay {
  background: rgba(var(--always-black-rgb), 0.65);
  animation: fade-in 250ms both;
}

.dialog-content {
  margin: auto;
  z-index: z("modal", "content");
  position: relative;
  background-color: var(--secondary);
  animation: fade-in 250ms both;
  box-shadow: var(--shadow-card);
  min-width: 40vw;
}

.dialog-body {
  overflow-y: auto;
  max-height: 400px;
  max-width: 800px;
  padding: 1em;
}

.dialog-header {
  display: flex;
  padding: 10px 15px;
  border-bottom: 1px solid var(--primary-low);
  align-items: center;

  h3 {
    font-size: var(--font-up-3);
    margin-bottom: 0;
  }

  .dialog-close {
    margin-left: auto;
    flex-basis: content;
    padding-left: 15px;
    .d-icon {
      color: var(--primary-high);
    }
  }
}

.dialog-footer {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  padding: 14px 15px 10px;
  border-top: 1px solid var(--primary-low);
  --btn-bottom-margin: 0.3em;
  .btn {
    margin: 0 0.75em var(--btn-bottom-margin) 0;
  }
}