*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }

:root {
    --bg: #12100c;
    --panel: #241f18;
    --line: #574a38;
    --text: #f7f0e4;
    --muted: #b9a891;
    --accent: #f0b429;
    --board: #2b2419;
    --cell: #38301f;
}

html, body { height: 100%; overscroll-behavior: none; }

body {
    position: fixed; inset: 0; overflow: hidden;
    color: var(--text);
    font-family: 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'Segoe UI', sans-serif;
    background:
        radial-gradient(circle at 50% 0%, rgba(240, 180, 41, 0.12), transparent 55%),
        linear-gradient(180deg, #0b0a07, #17140e);
    user-select: none; -webkit-user-select: none;
    -webkit-tap-highlight-color: transparent;
    touch-action: none;
}

.shell {
    display: flex; flex-direction: column;
    height: 100%; min-height: 100dvh;
    max-width: 480px; margin: 0 auto;
    padding:
        max(6px, env(safe-area-inset-top))
        max(8px, env(safe-area-inset-right))
        max(8px, env(safe-area-inset-bottom))
        max(8px, env(safe-area-inset-left));
}

.toolbar { display: flex; align-items: center; gap: 6px; flex: 0 0 auto; height: 38px; }
.toolbar-spacer { flex: 1; }

.icon-btn {
    display: inline-flex; align-items: center; justify-content: center;
    min-width: 34px; height: 31px; padding: 0 10px;
    border: 1px solid var(--line); border-radius: 9px;
    background: var(--panel); color: var(--text);
    font-family: inherit; font-size: 0.88rem; line-height: 1;
    text-decoration: none; cursor: pointer;
    transition: transform 0.12s ease, border-color 0.12s ease;
}

.icon-btn-text { font-size: 0.76rem; font-weight: 700; }
.icon-btn:active { transform: scale(0.94); border-color: var(--accent); }

.hud { display: flex; gap: 8px; flex: 0 0 auto; margin: 6px 0; }

.score-box {
    position: relative;
    flex: 1; display: flex; flex-direction: column; align-items: center;
    padding: 6px 4px; border-radius: 11px; background: var(--panel);
}

.score-box i { font-style: normal; font-size: 0.6rem; letter-spacing: 0.1em; color: var(--muted); }
.score-box b { font-size: 1.25rem; font-variant-numeric: tabular-nums; }

.gain {
    position: absolute; left: 50%; top: 4px;
    transform: translateX(-50%);
    font-size: 0.95rem; font-weight: 800; color: var(--accent);
    opacity: 0; pointer-events: none;
}

.gain.is-show { animation: rise 0.7s ease forwards; }

@keyframes rise {
    0% { opacity: 1; transform: translate(-50%, 0); }
    100% { opacity: 0; transform: translate(-50%, -26px); }
}

/* ===== Board ===== */
.board-area { flex: 1 1 auto; min-height: 0; display: flex; align-items: center; justify-content: center; }

.board {
    position: relative;
    border-radius: 12px;
    background: var(--board);
    touch-action: none;
}

.cells, .tiles { position: absolute; inset: 0; }

.cell-bg {
    position: absolute;
    border-radius: 8px;
    background: var(--cell);
}

.tile {
    position: absolute;
    display: flex; align-items: center; justify-content: center;
    border-radius: 8px;
    font-weight: 800;
    font-variant-numeric: tabular-nums;
    color: #2a2114;
    transition: transform 0.11s ease-out;
    will-change: transform;
}

.tile.is-new { animation: appear 0.14s ease-out; }
.tile.is-merged { animation: pop 0.16s ease-out; }

@keyframes appear { from { transform: scale(0.2); } }
@keyframes pop { 0% { transform: scale(1); } 50% { transform: scale(1.16); } 100% { transform: scale(1); } }

/* ===== Tools ===== */
.tools { display: flex; gap: 8px; flex: 0 0 auto; margin-top: 8px; }

.tool {
    flex: 1; min-height: 50px;
    display: flex; align-items: center; justify-content: center; gap: 8px;
    border: 1px solid var(--line); border-radius: 13px;
    background: var(--panel); color: var(--text);
    font-family: inherit; font-size: 0.9rem; font-weight: 700;
    cursor: pointer; transition: transform 0.1s ease;
}

.tool i { font-style: normal; font-size: 1.05rem; line-height: 1; }
.tool:active { transform: scale(0.97); }
.tool:disabled { opacity: 0.4; }

.hint { margin-top: 5px; text-align: center; font-size: 0.66rem; color: var(--muted); }

/* ===== Overlay ===== */
.overlay {
    position: absolute; inset: 0; display: none;
    align-items: center; justify-content: center; padding: 18px;
    background: rgba(8, 6, 4, 0.9);
    backdrop-filter: blur(5px); -webkit-backdrop-filter: blur(5px);
    z-index: 50;
}

.overlay.is-open { display: flex; }

.panel {
    width: 100%; max-width: 330px;
    display: flex; flex-direction: column; gap: 10px;
    padding: 22px 18px;
    border: 1px solid var(--line); border-radius: 20px;
    background: linear-gradient(180deg, #322a1e, #1c1810);
    text-align: center; animation: pop2 0.22s ease;
}

@keyframes pop2 { from { opacity: 0; transform: translateY(12px) scale(0.97); } to { opacity: 1; transform: none; } }

.panel-title { font-size: 1.6rem; font-weight: 800; letter-spacing: 0.06em; color: var(--accent); }

.btn {
    min-height: 46px; padding: 12px 20px;
    border: 1px solid var(--line); border-radius: 13px;
    background: rgba(255, 255, 255, 0.05); color: var(--text);
    font-family: inherit; font-size: 0.92rem; font-weight: 700;
    text-decoration: none; display: flex; align-items: center; justify-content: center;
    cursor: pointer;
}

.btn:active { transform: scale(0.97); }
.btn[hidden] { display: none; }
.btn-primary { border-color: transparent; background: linear-gradient(135deg, #ffd066, #e09a12); color: #2a1c00; }

.stat-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 7px; }
.stat { padding: 9px 6px; border-radius: 11px; background: rgba(255, 255, 255, 0.06); }
.stat b { display: block; font-size: 1.1rem; font-variant-numeric: tabular-nums; }
.stat span { font-size: 0.62rem; color: var(--muted); }

@media (max-height: 640px) {
    .hud { margin: 3px 0; }
    .score-box b { font-size: 1.05rem; }
    .tool { min-height: 44px; }
    .hint { display: none; }
}

@media (prefers-reduced-motion: reduce) {
    .tile, .panel { transition: none; animation: none; }
}