/* =============================================================
   GAME: Sliding Puzzle — glossy tiles in a periwinkle frame
   ============================================================= */
.board-sliding {
  --sl-glow: #7aa8ff;
  display: flex; flex-direction: column; align-items: center; gap: 12px;
}
.sl-frame {
  padding: 8px; border-radius: 18px;
  background: linear-gradient(160deg, #1d2c66, #0a1030 70%);
  box-shadow: 0 0 0 2px var(--sl-glow), 0 0 30px rgba(122, 168, 255, .35), inset 0 2px 12px rgba(0, 0, 0, .6), 0 12px 30px rgba(0, 0, 0, .4);
}
.sl-board {
  --n: 4;
  --cell: min(calc((100vw - 64px) / var(--n)), calc(372px / var(--n)));
  position: relative; width: calc(var(--cell) * var(--n)); height: calc(var(--cell) * var(--n));
  border-radius: 12px; touch-action: none; user-select: none; -webkit-user-select: none;
  background:
    linear-gradient(rgba(122, 168, 255, .07) 1px, transparent 1px) 0 0 / var(--cell) var(--cell),
    linear-gradient(90deg, rgba(122, 168, 255, .07) 1px, transparent 1px) 0 0 / var(--cell) var(--cell),
    #070b22;
  box-shadow: inset 0 3px 10px rgba(0, 0, 0, .7);
}
.sl-board:focus { outline: none; }
.sl-board:focus-visible { box-shadow: inset 0 3px 10px rgba(0, 0, 0, .7), 0 0 0 3px var(--focus); }
.sl-tile {
  position: absolute; left: 0; top: 0; width: var(--cell); height: var(--cell); padding: 3px; margin: 0; border: 0;
  background: none; cursor: default;
  transform: translate(calc(var(--x, 0) * var(--cell)), calc(var(--y, 0) * var(--cell)));
  transition: transform .13s cubic-bezier(.3, .7, .4, 1);
}
.sl-tile span {
  display: grid; place-items: center; width: 100%; height: 100%; border-radius: calc(var(--cell) * .14);
  background:
    radial-gradient(120% 70% at 30% 0%, rgba(255, 255, 255, .35), transparent 55%),
    linear-gradient(150deg, hsl(var(--h) 85% calc(var(--l) + 8%)), hsl(var(--h) 75% calc(var(--l) - 14%)));
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, .45), inset 0 -4px 0 rgba(0, 0, 0, .25), 0 3px 6px rgba(0, 0, 0, .45);
  color: #fff; font: 800 calc(var(--cell) * .4) / 1 var(--font-head); text-shadow: 0 2px 0 rgba(0, 0, 0, .3), 0 0 12px rgba(255, 255, 255, .25);
  transition: box-shadow .15s ease, filter .15s ease;
}
.sl-tile.sl-can { cursor: pointer; }
.sl-tile.sl-can:hover span { filter: brightness(1.12); }
.sl-tile:active span { filter: brightness(.95); }
.sl-tile:focus { outline: none; }
.sl-tile:focus-visible span { box-shadow: 0 0 0 3px var(--focus), inset 0 -4px 0 rgba(0, 0, 0, .25); }
/* tile sitting on its home square: small glowing pip */
.sl-tile.sl-home span::after {
  content: ""; position: absolute; right: calc(var(--cell) * .12); top: calc(var(--cell) * .12);
  width: max(5px, calc(var(--cell) * .07)); height: max(5px, calc(var(--cell) * .07)); border-radius: 50%;
  background: #fff; box-shadow: 0 0 6px #fff;
}
.sl-tile span { position: relative; }
.sl-tile:disabled { cursor: default; }
.sl-noanim .sl-tile { transition: none; }
.sl-still .sl-tile { transition-duration: .05s; }
/* last piece drops in when solved */
.sl-last { opacity: 0; pointer-events: none; }
.sl-last::before {
  content: ""; display: block; width: 100%; height: 100%; border-radius: calc(var(--cell) * .14);
  background:
    radial-gradient(120% 70% at 30% 0%, rgba(255, 255, 255, .35), transparent 55%),
    linear-gradient(150deg, hsl(var(--h) 85% calc(var(--l) + 8%)), hsl(var(--h) 75% calc(var(--l) - 14%)));
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, .45), inset 0 -4px 0 rgba(0, 0, 0, .25), 0 3px 6px rgba(0, 0, 0, .45);
}
.sl-won .sl-last { opacity: 1; animation: sldrop .45s cubic-bezier(.3, 1.5, .5, 1) .1s both; }
@keyframes sldrop { from { opacity: 0; transform: translate(calc(var(--x) * var(--cell)), calc(var(--y) * var(--cell))) scale(.3); } }
.sl-won .sl-tile span { animation: slwin 1s ease .2s both; }
@keyframes slwin { 40% { filter: brightness(1.35); box-shadow: 0 0 18px rgba(122, 168, 255, .8), inset 0 -4px 0 rgba(0, 0, 0, .25); } }
.sl-help { text-wrap: balance; margin: 0; font-size: .82rem; color: var(--muted); text-align: center; max-width: 420px; }
.sl-clock { font-variant-numeric: tabular-nums; }
.sl-best { color: var(--muted); font-weight: 600; }
@media (prefers-reduced-motion: reduce) {
  .sl-won .sl-last, .sl-won .sl-tile span { animation: none; }
}