papercss/src/components/_modals.scss

.modal{

  &:before{
    content: "";
    display: none;
    background: rgba(black,.6);
    position: fixed;
    top: 0; left: 0; right: 0; bottom: 0;
    z-index: 10;
  }

  &:target{
    &:before{
      display: flex;
    }
    .modal-body{
      @include translate(0, 0);
      top: 20%;
    }
  }

  .modal-body{
    flex: 1 1 auto;
    padding: 1.25rem;
    background: $white;
    border: 2px solid $muted-light;
    word-wrap: break-word;
    position: fixed;
    z-index: 11;
    max-width: 960px;
    @include translate(0, -5000%);
    @include transition(transform);

    @include resp(medium) {
      max-width: 85%;
    }
    @include resp(xsmall) {
      max-width: 90%;
    }
  }

  .btn-close{
    color: $primary-light;
    font-size: 30px;
    text-decoration: none;
    position: absolute; right: 0; top: 0;
    @extend .margin;
    background: inherit;
    &:hover{
      color: $muted;
    }
  }

  .modal-title, h4 {
    margin-top: 0;
    margin-bottom: 0.5rem;
  }

  .modal-subtitle, h5 {
    @extend .text-secondary;
    margin-top: 0;
    margin-bottom: 0.5rem;
  }

  .modal-text, p {
    margin-top: 0;
    margin-bottom: 1rem;
  }

  .modal-link + .modal-link,
  a + a {
    margin-left: 1.25rem;
  }

  a button {
    text-decoration: none;
    background: $white;
  }
}