/*
 * Placeholdery z Bootstrapu 5.3 (https://getbootstrap.com/docs/5.3/components/placeholders/).
 * Projekt jede na Bootstrapu 5.0, který je ještě nemá — bez tohohle by
 * kostry stránek (#[LazyPage]) a načítané bloky zůstaly prázdné.
 */
.placeholder {
  display: inline-block;
  min-height: 1em;
  vertical-align: middle;
  cursor: wait;
  background-color: currentcolor;
  opacity: .5;
}
.placeholder.btn::before {
  display: inline-block;
  content: "";
}
.placeholder-xs { min-height: .6em; }
.placeholder-sm { min-height: .8em; }
.placeholder-lg { min-height: 1.2em; }

.placeholder-glow .placeholder {
  animation: placeholder-glow 2s ease-in-out infinite;
}
@keyframes placeholder-glow {
  50% { opacity: .2; }
}

.placeholder-wave {
  -webkit-mask-image: linear-gradient(130deg, #000 55%, rgba(0, 0, 0, .8) 75%, #000 95%);
  mask-image: linear-gradient(130deg, #000 55%, rgba(0, 0, 0, .8) 75%, #000 95%);
  -webkit-mask-size: 200% 100%;
  mask-size: 200% 100%;
  animation: placeholder-wave 2s linear infinite;
}
@keyframes placeholder-wave {
  100% {
    -webkit-mask-position: -200% 0%;
    mask-position: -200% 0%;
  }
}

@media (prefers-reduced-motion: reduce) {
  .placeholder-glow .placeholder,
  .placeholder-wave { animation: none; }
}