:root{--ink:#20201d;--muted:#74736d;--paper:#f5f2e9;--card:#fffdfa;--accent:#ce5d32;--dark:#485748;--light:#d9d2bd;--line:#ddd8cb;--shadow:0 18px 50px #382b1b18}*{box-sizing:border-box}body{margin:0;background:var(--paper);color:var(--ink);font:15px/1.45 ui-sans-serif,system-ui,-apple-system,sans-serif}header{height:74px;border-bottom:1px solid var(--line);display:flex;align-items:center;justify-content:space-between;padding:0 max(22px,calc((100vw - 1120px)/2));background:#faf8f2}.brand{display:flex;align-items:center;gap:11px}.brand div{display:flex;flex-direction:column;line-height:1.05}.brand strong{font:700 22px Georgia,serif}.brand small{color:var(--muted);letter-spacing:.08em;text-transform:uppercase;font-size:9px;margin-top:4px}.mark{width:38px;height:38px;border-radius:50%;display:grid;place-items:center;background:var(--accent);color:white;font:700 20px Georgia}.model{font-size:12px;color:var(--muted);border:1px solid var(--line);border-radius:99px;padding:7px 11px}main{max-width:1120px;margin:38px auto;padding:0 22px;display:grid;grid-template-columns:minmax(320px,620px) minmax(300px,380px);gap:48px;align-items:start}.board-column{min-width:0}.board{width:100%;aspect-ratio:1;display:grid;grid-template-columns:repeat(8,1fr);box-shadow:var(--shadow);border-radius:5px;overflow:hidden}.square{border:0;border-radius:0;padding:0;position:relative;display:grid;place-items:center;font-size:clamp(30px,6vw,58px);line-height:1;cursor:pointer}.square.light{background:var(--light)}.square.dark{background:var(--dark)}.square.selected{box-shadow:inset 0 0 0 5px #e9a641}.square.target:after{content:"";position:absolute;width:22%;aspect-ratio:1;border-radius:50%;background:#e9a641bb}.square.capture:after{width:78%;background:transparent;border:5px solid #e9a641aa}.coord{position:absolute;font:bold 10px system-ui;opacity:.65}.file{bottom:3px;right:4px}.rank{top:3px;left:4px}.light .coord{color:var(--dark)}.dark .coord{color:var(--light)}.actions{display:flex;gap:8px;flex-wrap:wrap;margin-top:16px}.actions button,.secondary{background:transparent;border:1px solid var(--line);color:var(--ink)}button{font:inherit;border-radius:7px;padding:9px 12px;cursor:pointer}button:hover{filter:brightness(.96)}button:disabled{opacity:.5;cursor:wait}.status{margin-top:13px;color:var(--muted)}aside{display:grid;gap:13px}.panel{background:var(--card);border:1px solid var(--line);border-radius:11px;padding:17px;box-shadow:0 5px 18px #392b1810}.panel-title{display:flex;justify-content:space-between;align-items:center;margin-bottom:12px;font-weight:650}.panel-title small{font-weight:400;color:var(--muted)}textarea{width:100%;resize:vertical;border:1px solid var(--line);border-radius:7px;background:#faf8f1;padding:10px;font:12px/1.45 ui-monospace,monospace}.wide{width:100%;margin-top:9px}.primary{border:0;color:white;background:var(--accent);font-weight:650;padding:11px}.link{border:0;background:none;color:var(--accent);padding:0;font-size:12px}.panel label{display:flex;justify-content:space-between;font-weight:600}.panel output{color:var(--accent)}input[type=range]{width:100%;accent-color:var(--accent);margin:12px 0}details{margin:3px 0 11px;border-top:1px solid var(--line);padding-top:10px}summary{cursor:pointer;color:var(--muted);margin-bottom:12px}.suggestions{display:grid;gap:7px}.suggestion{display:grid;grid-template-columns:36px 1fr auto;align-items:center;gap:9px;border:1px solid var(--line);background:#faf8f1;text-align:left;padding:9px 10px}.suggestion b{font:700 18px Georgia,serif}.suggestion .bar{height:4px;background:var(--line);border-radius:3px;margin-top:5px}.suggestion .fill{height:100%;background:var(--accent);border-radius:3px}.suggestion em{font-style:normal;color:var(--muted)}.empty,.moves{color:var(--muted);margin:4px 0}.moves{font-family:ui-monospace,monospace;max-height:90px;overflow:auto}.notice{background:#fff0d6;border:1px solid #e8c789;border-radius:9px;padding:11px 14px;margin-bottom:14px;display:flex;flex-direction:column}.notice span{font-size:12px;color:#755e36}.hidden{display:none}.error{color:#b22e26;margin:8px 0 0;font-size:12px}footer{max-width:1120px;margin:10px auto 30px;padding:22px;border-top:1px solid var(--line);display:flex;justify-content:space-between;color:var(--muted);font-size:12px}a{color:var(--accent)}@media(max-width:820px){main{grid-template-columns:1fr;gap:25px;margin-top:22px}.board-column{max-width:620px;margin:auto;width:100%}aside{max-width:620px;margin:auto;width:100%}footer{flex-direction:column;gap:8px}.model{display:none}}
/* Opening Drill's accepted chess treatment: Cburnett pieces and Study board palette. */
:root{--ink:#17231e;--muted:#667069;--paper:#f3efe6;--card:#fffcf6;--dark:#718268;--light:#e7d9ba;--line:#ded6c7;--shadow:0 14px 36px #382b1b18}
main{max-width:1060px;grid-template-columns:minmax(320px,560px) minmax(300px,400px);gap:42px}
.board{max-width:560px;grid-template-columns:repeat(8,minmax(0,1fr));grid-template-rows:repeat(8,minmax(0,1fr));border:1px solid #594d3b33;border-radius:7px;box-shadow:var(--shadow)}
.square{min-width:0;min-height:0;font-size:0;overflow:hidden}
.piece{display:block;width:82%;height:82%;object-fit:contain;position:relative;z-index:2;pointer-events:none;user-select:none}
.square.selected{box-shadow:inset 0 0 0 4px #c4933e}
.square.target:after{width:20%;background:#c4933ecc;z-index:3}
.square.capture:after{width:76%;border:4px solid #c4933ecc;z-index:3}
.pgn-help{margin:9px 0 0;color:var(--muted);font-size:12px}
.move-tree{display:flex;align-items:center;flex-wrap:wrap;gap:5px;line-height:1.8}
.move-chip{border:0;background:transparent;border-radius:6px;padding:3px 6px;color:var(--muted);font:600 14px ui-monospace,monospace}
.move-chip:hover{background:#e7d9ba66;color:var(--ink)}
.move-chip.current{background:var(--accent);color:white}
.move-chip.start{font-family:ui-sans-serif,system-ui,sans-serif}
.variation{display:inline-flex;align-items:center;flex-wrap:wrap;gap:3px;color:#958a7a;background:#f3efe6;border-radius:7px;padding:1px 4px}
.engine-lines{display:grid;gap:7px}
.engine-line{display:grid;grid-template-columns:24px auto 1fr;grid-template-areas:"rank move score" "rank pv pv";align-items:center;gap:2px 9px;border:1px solid var(--line);background:#faf8f1;text-align:left;padding:9px 10px;min-width:0}
.engine-rank{grid-area:rank;color:var(--muted)}
.engine-line strong{grid-area:move;font:700 18px Georgia,serif}
.engine-line em{grid-area:score;justify-self:end;font-style:normal;font-weight:700;color:var(--accent)}
.engine-line small{grid-area:pv;color:var(--muted);white-space:nowrap;overflow:hidden;text-overflow:ellipsis;min-width:0}

/* Phones should feel like an app, not a desktop page squeezed into a viewport. */
@media(max-width:520px){
  html,body{max-width:100%;overflow-x:hidden}
  header{height:58px;padding:0 14px}
  .mark{width:34px;height:34px;font-size:18px}
  .brand strong{font-size:20px}
  main{width:100%;min-width:0;grid-template-columns:minmax(0,1fr);margin:12px auto 20px;padding:0 14px;gap:16px}
  .board-column,aside{width:100%;min-width:0;max-width:none;margin:0}
  .board{width:min(100%,calc(100vw - 28px));max-width:none;box-shadow:0 8px 22px #382b1b18}
  .actions{display:grid;grid-template-columns:repeat(4,minmax(0,1fr)) 1.45fr;gap:6px;margin-top:10px}
  .actions button{min-width:0;min-height:44px;padding:8px 4px;font-size:18px}
  .actions #flip{font-size:15px;white-space:nowrap}
  aside{gap:10px}
  .panel{padding:14px;border-radius:9px}
  .history{min-height:74px}
  .suggestion{min-height:46px}
  input[type=range]{min-height:30px;margin:8px 0 12px}
  textarea{font-size:16px}
  footer{margin:0 14px 20px;padding:16px 0}
}