Bootstrap/scss/_toasts.scss

.toast {
  max-width: $toast-max-width;
  overflow: hidden; // cheap rounded corners on nested items
  font-size: $toast-font-size; // knock it down to 14px
  background-color: $toast-background-color;
  background-clip: padding-box;
  border: $toast-border-width solid $toast-border-color;
  border-radius: $toast-border-radius;
  box-shadow: $toast-box-shadow;
  backdrop-filter: blur(10px);
  opacity: 0;

  + .toast {
    margin-top: $toast-padding-x;
  }

  &.showing {
    opacity: 1;
  }

  &.show {
    display: block;
    opacity: 1;
  }

  &.hide {
    display: none;
  }
}

.toast-header {
  display: flex;
  align-items: center;
  padding: $toast-padding-y $toast-padding-x;
  color: $toast-header-color;
  background-color: $toast-header-background-color;
  background-clip: padding-box;
  border-bottom: $toast-border-width solid $toast-header-border-color;
}

.toast-body {
  padding: $toast-padding-x; // apply to both vertical and horizontal
}