/* ╔══════════════════════════════════════════════════════════════╗
   ║ 🎨 SKELETON LOADER + OPTIMISTIC UI — Mục 13+14               ║
   ║                                                                ║
   ║ Use cases:                                                     ║
   ║   <div class="x-skel x-skel-card"></div>      — card placeholder
   ║   <div class="x-skel x-skel-text"></div>      — text placeholder
   ║   <div class="x-skel x-skel-avatar"></div>    — circular avatar
   ║   <div class="x-skel x-skel-thumbnail"></div> — 16:9 video thumb
   ║                                                                ║
   ║ Optimistic UI:                                                 ║
   ║   .x-optimistic        — pending state (50% opacity)          ║
   ║   .x-optimistic-error  — flash red khi rollback               ║
   ╚══════════════════════════════════════════════════════════════*/

@keyframes x-skel-shimmer {
  0%   { background-position: -200% 0; }
  100% { background-position:  200% 0; }
}

.x-skel {
  background: linear-gradient(
    90deg,
    rgba(255,255,255,0.04) 0%,
    rgba(255,255,255,0.10) 50%,
    rgba(255,255,255,0.04) 100%
  );
  background-size: 200% 100%;
  animation: x-skel-shimmer 1.4s ease-in-out infinite;
  border-radius: 6px;
  display: block;
  /* GPU layer cho mượt */
  will-change: background-position;
  transform: translateZ(0);
}

/* Light mode */
:root:not(.dark) .x-skel {
  background: linear-gradient(
    90deg,
    rgba(0,0,0,0.04) 0%,
    rgba(0,0,0,0.10) 50%,
    rgba(0,0,0,0.04) 100%
  );
  background-size: 200% 100%;
}

/* ─── Variants ─── */
.x-skel-text {
  height: 12px;
  margin: 4px 0;
}
.x-skel-text-lg {
  height: 18px;
}
.x-skel-text-sm {
  height: 8px;
}
.x-skel-line-50  { width: 50%; }
.x-skel-line-75  { width: 75%; }
.x-skel-line-90  { width: 90%; }
.x-skel-line-100 { width: 100%; }

.x-skel-avatar {
  width: 40px;
  height: 40px;
  border-radius: 50%;
}
.x-skel-avatar-sm {
  width: 28px; height: 28px;
}
.x-skel-avatar-lg {
  width: 56px; height: 56px;
}

.x-skel-thumbnail {
  aspect-ratio: 16 / 9;
  width: 100%;
  border-radius: 12px;
}

.x-skel-card {
  /* Wrapper: tạo card với thumbnail + 2 lines text */
  padding: 0;
  background: transparent !important;
  animation: none;
}
.x-skel-card .x-skel-body {
  padding: 12px 4px 0;
}

.x-skel-circle {
  border-radius: 50%;
}

.x-skel-pill {
  height: 28px;
  border-radius: 999px;
}

.x-skel-button {
  height: 36px;
  border-radius: 8px;
  width: 100%;
}

/* ─── Optimistic UI states ─── */
.x-optimistic {
  opacity: 0.55;
  filter: saturate(0.7);
  position: relative;
  pointer-events: none;
  transition: opacity 0.2s, filter 0.2s;
}
.x-optimistic::after {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(90deg,
    transparent 0%,
    rgba(255,255,255,0.08) 50%,
    transparent 100%);
  background-size: 200% 100%;
  animation: x-skel-shimmer 1s ease-in-out infinite;
  pointer-events: none;
  border-radius: inherit;
}
.x-optimistic-success {
  opacity: 1;
  filter: none;
  animation: x-flash-success 0.5s ease-out;
}
.x-optimistic-error {
  animation: x-flash-error 0.4s ease-out;
}
@keyframes x-flash-success {
  0%   { background-color: rgba(16, 185, 129, 0.25); }
  100% { background-color: transparent; }
}
@keyframes x-flash-error {
  0%, 100% { transform: translateX(0); }
  20%, 60% { transform: translateX(-4px); background-color: rgba(239, 68, 68, 0.18); }
  40%, 80% { transform: translateX(4px); }
}

/* ─── Reduced motion: tắt shimmer ─── */
@media (prefers-reduced-motion: reduce) {
  .x-skel, .x-optimistic::after { animation: none !important; }
}