:root{--bg: #faf8ef;--text: #776e65;--board-bg: #bbada0;--cell-bg: #cdc1b4;--accent: #8f7a66;--accent-hover: #9f8b77;--panel-bg: #ffffff;--panel-border: #e6ddd3;--best: #edc22e;color-scheme:light}*{box-sizing:border-box}body{margin:0;font-family:Segoe UI,Helvetica Neue,Arial,sans-serif;background:var(--bg);color:var(--text);-webkit-font-smoothing:antialiased}#app{max-width:1080px;margin:0 auto;padding:24px 16px 48px}.app-header h1{margin:0;font-size:2.6rem;font-weight:800}.app-header .subtitle{font-size:1.1rem;font-weight:600;color:var(--accent)}.tagline{margin:4px 0 20px;max-width:40ch;color:#9a8f82}.layout{display:grid;grid-template-columns:minmax(280px,460px) minmax(280px,1fr);gap:24px;align-items:start}@media (max-width: 820px){.layout{grid-template-columns:1fr}}.scoreboard{display:flex;align-items:center;gap:12px;margin-bottom:16px}.score-box{display:flex;flex-direction:column;align-items:center;min-width:84px;padding:8px 12px;border-radius:6px;background:var(--board-bg);color:#fff}.score-label{font-size:.7rem;text-transform:uppercase;letter-spacing:.08em;font-weight:700;opacity:.85}.score-value{font-size:1.5rem;font-weight:800}.btn{margin-left:auto;padding:10px 16px;border:none;border-radius:6px;background:var(--accent);color:#fff;font-weight:700;cursor:pointer;transition:background .15s ease}.btn:hover{background:var(--accent-hover)}.btn.secondary{margin-left:0;background:#bbada0}.btn.secondary:hover{background:#a99a8b}.btn.secondary.active{background:#edc22e;color:#6b5c14}.controls{display:flex;align-items:center;gap:16px;margin-top:16px}.speed{display:flex;align-items:center;gap:8px;font-size:.8rem;font-weight:600;color:#9a8f82}.speed input[type=range]{accent-color:var(--accent);cursor:pointer}.board{position:relative;width:100%;aspect-ratio:1 / 1;background:var(--board-bg);border-radius:8px;overflow:hidden;touch-action:none;-webkit-user-select:none;user-select:none}.grid-bg{position:absolute;top:0;right:0;bottom:0;left:0;display:grid;grid-template-columns:repeat(4,1fr);grid-template-rows:repeat(4,1fr)}.cell{position:relative}.cell:after{content:"";position:absolute;top:8%;right:8%;bottom:8%;left:8%;border-radius:6px;background:var(--cell-bg)}.tile-layer{position:absolute;top:0;right:0;bottom:0;left:0}.tile{position:absolute;top:0;left:0;width:25%;height:25%;display:flex;align-items:center;justify-content:center;transition:transform .11s ease-in-out;will-change:transform;color:var(--tile-color, #776e65);font-weight:800;font-size:calc(min(460px,46vw) / 4 * .42 * var(--tile-font-scale, 1))}.tile:before{content:"";position:absolute;top:8%;right:8%;bottom:8%;left:8%;border-radius:6px;background:var(--tile-bg, #eee4da);z-index:-1}.tile[data-value="2"]{--tile-bg: #eee4da;--tile-color: #776e65}.tile[data-value="4"]{--tile-bg: #ede0c8;--tile-color: #776e65}.tile[data-value="8"]{--tile-bg: #f2b179;--tile-color: #f9f6f2}.tile[data-value="16"]{--tile-bg: #f59563;--tile-color: #f9f6f2}.tile[data-value="32"]{--tile-bg: #f67c5f;--tile-color: #f9f6f2}.tile[data-value="64"]{--tile-bg: #f65e3b;--tile-color: #f9f6f2}.tile[data-value="128"]{--tile-bg: #edcf72;--tile-color: #f9f6f2}.tile[data-value="256"]{--tile-bg: #edcc61;--tile-color: #f9f6f2}.tile[data-value="512"]{--tile-bg: #edc850;--tile-color: #f9f6f2}.tile[data-value="1024"]{--tile-bg: #edc53f;--tile-color: #f9f6f2}.tile[data-value="2048"]{--tile-bg: #edc22e;--tile-color: #f9f6f2}.tile[data-value="4096"],.tile[data-value="8192"],.tile[data-value="16384"]{--tile-bg: #3c3a32;--tile-color: #f9f6f2}@keyframes pop-spawn{0%{transform-origin:center;opacity:0}60%{opacity:1}}@keyframes pop-merge{0%{scale:1}50%{scale:1.18}to{scale:1}}.tile.pop-spawn:before{animation:pop-spawn .16s ease-out}.tile.pop-merge:before{animation:pop-merge .16s ease-out}.board-overlay{position:absolute;top:0;right:0;bottom:0;left:0;display:flex;align-items:center;justify-content:center;font-size:2rem;font-weight:800;color:var(--text);background:#eee4dab8;z-index:10;transition:opacity .3s ease}.board-overlay.won{color:#f9f6f2;background:#edc22ec7}.board-overlay.hidden{opacity:0;pointer-events:none}.math-panel{background:var(--panel-bg);border:1px solid var(--panel-border);border-radius:8px;padding:18px 20px;min-height:200px}.placeholder{color:#b3a99d;font-style:italic}.math-heading h2{margin:0 0 2px;font-size:1.1rem}.math-heading p{margin:0 0 16px;font-size:.82rem;color:#9a8f82}.move-rows{display:flex;flex-direction:column;gap:8px}.move-row{display:grid;grid-template-columns:64px 1fr 72px 64px;align-items:center;gap:10px;padding:6px 8px;border-radius:6px;font-variant-numeric:tabular-nums;transition:background .2s ease}.move-row.best{background:#edc22e29}.move-row.illegal{opacity:.4}.move-label{display:flex;align-items:center;gap:6px;font-weight:700}.move-arrow{font-size:1.2rem;color:var(--accent)}.move-name{font-size:.85rem}.ev-bar{position:relative;height:14px;border-radius:7px;background:#efe9e1;overflow:hidden}.ev-fill{position:absolute;inset:0 auto 0 0;width:0;border-radius:7px;background:linear-gradient(90deg,#bbada0,#8f7a66);transition:width .25s ease}.move-row.best .ev-fill{background:linear-gradient(90deg,#edc850,#edc22e)}.ev-value{text-align:right;font-weight:700;font-size:.9rem}.ev-delta{text-align:right;font-size:.78rem;color:#9a8f82}.move-row.best .ev-delta{color:#bf9c1c;font-weight:700}.recommendation{margin-top:16px;font-size:.95rem}.recommendation strong{color:var(--accent);font-size:1.05rem}.recommendation.terminal{color:#c0392b;font-weight:700}.chance-summary,.search-stats{margin-top:8px;font-size:.76rem;color:#9a8f82;font-variant-numeric:tabular-nums}.search-stats{font-family:SFMono-Regular,Consolas,monospace;color:#b0a596}.move-hint{position:absolute;z-index:8;font-size:2.2rem;font-weight:800;color:#8f7a66e6;text-shadow:0 0 12px rgba(237,194,46,.9);pointer-events:none;animation:hint-pulse 1.2s ease-in-out infinite}.move-hint.hidden{display:none}.move-hint[data-dir=up]{top:4px;left:50%;transform:translate(-50%)}.move-hint[data-dir=down]{bottom:4px;left:50%;transform:translate(-50%)}.move-hint[data-dir=left]{left:6px;top:50%;transform:translateY(-50%)}.move-hint[data-dir=right]{right:6px;top:50%;transform:translateY(-50%)}@keyframes hint-pulse{0%,to{opacity:.45}50%{opacity:1}}