@import url("https://fonts.googleapis.com/css2?family=Inter:wght@400;500;700;800&display=swap");

    :root {
      --bg: #000;
      --board: #14141c;
      --cell: #20202c;
      --text: #fff;
      --muted: #999;
      --accent: #3c6dec;
      --gap: 12px;
    }

    * {
      box-sizing: border-box;
      -webkit-tap-highlight-color: transparent;
    }

    html,
    body {
      margin: 0;
      background: var(--bg);
      color: var(--text);
      font-family: "Inter", sans-serif;
      touch-action: manipulation;
    }

    .wrap {
      min-height: 100vh;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      padding: 1.25rem 1rem 2rem;
      gap: 1rem;
    }

    .back-link {
      position: fixed;
      top: 12px;
      left: 12px;
      z-index: 50;
      display: inline-block;
      color: #fff;
      background: var(--accent);
      text-decoration: none;
      font-weight: 700;
      font-size: 0.85rem;
      padding: 6px 12px;
      border-radius: 8px;
    }
    .back-link:hover {
      filter: brightness(1.12);
    }

    .topbar {
      width: 100%;
      max-width: 460px;
      display: flex;
      align-items: flex-end;
      justify-content: space-between;
      gap: 1rem;
    }

    .title {
      font-size: 2.75rem;
      font-weight: 800;
      margin: 0;
      line-height: 1;
    }
    .subtitle {
      margin: 0.4rem 0 0;
      color: var(--muted);
      font-size: 0.9rem;
    }

    .scores {
      display: flex;
      gap: 0.6rem;
    }
    .score-box {
      background: var(--board);
      border-radius: 10px;
      padding: 0.45rem 0.9rem;
      text-align: center;
      min-width: 78px;
    }
    .score-box .label {
      font-size: 0.65rem;
      letter-spacing: 0.08em;
      text-transform: uppercase;
      color: var(--muted);
      font-weight: 700;
    }
    .score-box .val {
      font-size: 1.4rem;
      font-weight: 800;
      display: inline-block;       /* so the pop scales tightly around the number */
      transform-origin: center;
    }
    .score-box .val.pop { animation: pop 0.18s ease; }

    .controls {
      width: 100%;
      max-width: 460px;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 0.6rem;
    }
    .hint {
      color: var(--muted);
      font-size: 0.85rem;
    }
    .btn {
      cursor: pointer;
      background: var(--accent);
      color: #fff;
      border: none;
      border-radius: 8px;
      padding: 0.6rem 1.1rem;
      font-family: inherit;
      font-size: 0.95rem;
      font-weight: 700;
      transition: filter 0.15s ease;
    }
    .btn:hover {
      filter: brightness(1.12);
    }

    .board-wrap {
      position: relative;
      width: 100%;
      max-width: 460px;
    }
    .board {
      position: relative;
      width: 100%;
      aspect-ratio: 1 / 1;
      background: var(--board);
      border-radius: 12px;
      --cells: 4;
      touch-action: none; /* swipes control the game, never scroll the page */
    }
    .grid-bg {
      position: absolute;
      inset: var(--gap);
      display: grid;
      grid-template-columns: repeat(var(--cells), 1fr);
      grid-template-rows: repeat(var(--cells), 1fr);
      gap: var(--gap);
    }
    .grid-bg .cell {
      background: var(--cell);
      border-radius: 8px;
    }
    .tiles {
      position: absolute;
      inset: var(--gap);
      pointer-events: none;
    }

    /* The OUTER .tile is absolutely positioned and animates its transform
       (the slide). The INNER element handles spawn/merge "pop" scaling, so
       the slide and the pop never fight over the same transform. */
    .tile {
      position: absolute;
      top: 0;
      left: 0;
      z-index: 2;
      transition: transform 90ms ease-in-out;
      will-change: transform;
    }
    .tiles.no-anim .tile {
      transition: none;
    }
    .tile-inner {
      width: 100%;
      height: 100%;
      display: flex;
      align-items: center;
      justify-content: center;
      border-radius: 8px;
      font-weight: 800;
      font-size: clamp(1.1rem, 7vw, 2rem);
      color: #fff;
      background: #2a2a38;
    }
    .tile-inner.appear {
      animation: appear 0.14s ease;
    }
    .tile-inner.pop {
      animation: pop 0.18s ease;
    }
    @keyframes appear {
      from {
        transform: scale(0.3);
        opacity: 0;
      }
      to {
        transform: scale(1);
        opacity: 1;
      }
    }
    @keyframes pop {
      0% {
        transform: scale(1);
      }
      55% {
        transform: scale(1.18);
      }
      100% {
        transform: scale(1);
      }
    }

    /* Classic 2048 tile palette (selectors live on .tile-inner) */
    .t2 { background: #3a3f4b; }
    .t4 { background: #45506b; }
    .t8 { background: #d97a3a; }
    .t16 { background: #e06c2e; }
    .t32 { background: #ec5d3a; }
    .t64 { background: #f24a2c; }
    .t128 { background: #edc850; color: #1a1a1a; font-size: clamp(1rem, 6vw, 1.7rem); }
    .t256 { background: #edc342; color: #1a1a1a; font-size: clamp(1rem, 6vw, 1.7rem); }
    .t512 { background: #edbd2f; color: #1a1a1a; font-size: clamp(1rem, 6vw, 1.7rem); }
    .t1024 { background: #edb91c; color: #1a1a1a; font-size: clamp(0.85rem, 5vw, 1.4rem); }
    .t2048 { background: #f5c518; color: #1a1a1a; font-size: clamp(0.85rem, 5vw, 1.4rem); box-shadow: 0 0 22px rgba(245, 197, 24, 0.6); }
    .t-big { background: #111; color: #f5c518; border: 2px solid #f5c518; font-size: clamp(0.8rem, 4.5vw, 1.3rem); }

    .overlay {
      position: absolute;
      inset: 0;
      z-index: 10; /* above the tiles (which use z-index up to 3) */
      display: none;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      gap: 0.8rem;
      background: rgba(10, 10, 14, 0.86);
      border-radius: 12px;
      text-align: center;
      padding: 1rem;
    }
    .overlay.show {
      display: flex;
    }
    .overlay h2 {
      margin: 0;
      font-size: 2rem;
      font-weight: 800;
    }
    .overlay p {
      margin: 0;
      color: var(--muted);
    }
    .overlay .btn-row {
      display: flex;
      gap: 0.6rem;
      flex-wrap: wrap;
      justify-content: center;
    }
    .btn.ghost {
      background: transparent;
      border: 1px solid #444;
    }

    #byline {
      color: #666;
      font-size: 75%;
      margin-top: 0.5rem;
    }
    /* Accessibility: honor prefers-reduced-motion — neutralize animations,
   transitions, and motion effects (pulse, shake, drop, blink, glows). */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
    scroll-behavior: auto !important;
  }
}