/* Board themes and piece sets. Each is scoped to an attribute so a swatch can
   preview a theme by carrying the attribute itself. */
:root,[data-board="garden"]{--sq-light:#ecebdc;--sq-dark:#93a585;--sq-last-light:#e3d892;--sq-last-dark:#b4b56f;--sq-sel-light:#e0c46c;--sq-sel-dark:#c4ac55;--frame-bg:#e3e5d9;--frame-line:#c7cfc0;--frame-ink:#65716a;--dot:#30594b70;--arrow:#c0821f}
[data-board="ocean"]{--sq-light:#e4eff3;--sq-dark:#6f9db3;--sq-last-light:#f4e9a6;--sq-last-dark:#a9b98a;--sq-sel-light:#ffd889;--sq-sel-dark:#d9b25c;--frame-bg:#d7e5eb;--frame-line:#b2c9d3;--frame-ink:#4d6b78;--dot:#1f4e6680;--arrow:#e07a5f}
[data-board="candy"]{--sq-light:#fdeef3;--sq-dark:#e7a3be;--sq-last-light:#fff1a8;--sq-last-dark:#f0c38f;--sq-sel-light:#ffd36e;--sq-sel-dark:#eeb05a;--frame-bg:#fbe1eb;--frame-line:#eec0d1;--frame-ink:#9a5874;--dot:#8c3a6080;--arrow:#7b5cd6}
[data-board="walnut"]{--sq-light:#f0d9b5;--sq-dark:#b58863;--sq-last-light:#f4e38a;--sq-last-dark:#d2b14e;--sq-sel-light:#f7ec74;--sq-sel-dark:#dac34b;--frame-bg:#e6d1b1;--frame-line:#c6a77e;--frame-ink:#7a5a3a;--dot:#4a2d1680;--arrow:#2f7a52}
[data-board="midnight"]{--sq-light:#c6cfe0;--sq-dark:#5b6a8c;--sq-last-light:#e5d68a;--sq-last-dark:#9a9867;--sq-sel-light:#f0d36b;--sq-sel-dark:#c4a74f;--frame-bg:#2b3245;--frame-line:#1b2131;--frame-ink:#aab4cc;--dot:#10182b90;--arrow:#f2a65a}
:root,[data-pieces="classic"]{--pw-fill:#fffdf5;--pw-line:#2a2a26;--pb-fill:#1d2421;--pb-line:#1d2421}
[data-pieces="marble"]{--pw-fill:#ffffff;--pw-line:#56607a;--pb-fill:#2e3a57;--pb-line:#16203a}
[data-pieces="jade"]{--pw-fill:#f6e2a6;--pw-line:#6b4f12;--pb-fill:#2f6b55;--pb-line:#143a2c}
[data-pieces="candy"]{--pw-fill:#fff4fa;--pw-line:#b04a7c;--pb-fill:#6c4ab6;--pb-line:#3b2270}
[data-pieces="ember"]{--pw-fill:#ffe9c7;--pw-line:#a2461f;--pb-fill:#7a2a1c;--pb-line:#3e130b}
:root{font-family:Inter,ui-sans-serif,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;color:#283d35;background:#f3f1e9;font-synthesis:none;--ink:#283d35;--muted:#65716a;--line:#dcded2;--paper:#faf9f4;--green:#30594b;--gold:#c29547;--danger:#a0442d;--good:#2f7a52}
*{box-sizing:border-box}
body{margin:0;background:#f3f1e9}
button,select,input{font:inherit;color:inherit}
button{cursor:pointer;-webkit-tap-highlight-color:transparent}
button:disabled{cursor:default;opacity:.45}
button:focus-visible,a:focus-visible,select:focus-visible{outline:3px solid #c08033;outline-offset:3px}
[hidden]{display:none!important}

.page-shell{max-width:1220px;margin:auto;padding:0 42px}
.site-header{min-height:92px;display:flex;align-items:center;justify-content:space-between;border-bottom:1px solid var(--line);gap:24px}
.brand{display:flex;align-items:center;gap:12px;text-decoration:none;color:inherit;font-family:Georgia,serif;font-size:24px;font-weight:bold;letter-spacing:-.6px}
.brand-mark{width:44px;height:44px;display:grid;place-items:center;border-radius:12px;background:var(--ink);color:#f2e8c7;font-size:30px}
.brand small{display:block;font:9px/1.7 ui-sans-serif,sans-serif;letter-spacing:2.4px;font-weight:600;margin-top:4px;color:var(--muted)}
.progress-pill{font-size:10px;letter-spacing:1.3px;font-weight:600;color:var(--green);border:1px solid #bfc8bb;border-radius:20px;padding:7px 12px}

.intro{display:flex;align-items:end;justify-content:space-between;gap:32px;margin:34px 0 24px}
.intro>p{font-size:12px;line-height:1.8;color:var(--muted);margin:0 0 2px;text-align:right}
.eyebrow{font-size:9px;font-weight:700;letter-spacing:1.8px;line-height:1.7;color:var(--muted);margin:0 0 8px}
h1{font-family:Georgia,"Times New Roman",serif;font-weight:normal;font-size:clamp(28px,3.4vw,42px);letter-spacing:-1.3px;margin:0;line-height:1.1}
h2,h3{font-family:Georgia,serif;font-weight:normal;letter-spacing:-.3px}
.muted{color:var(--muted)}
.small{font-size:12px;line-height:1.6}

.button{min-height:40px;padding:9px 15px;border:1px solid #bfc8bb;border-radius:7px;background:transparent;font-size:12px;font-weight:600;display:inline-flex;align-items:center;justify-content:center;gap:10px;transition:background .15s}
.button:hover:not(:disabled){background:#e5e9dd}
.button.primary{background:var(--green);color:#fff;border-color:var(--green)}
.button.primary:hover:not(:disabled){background:#223f35}
.button.small{min-height:32px;padding:6px 11px;font-size:11px}
.icon-button{width:40px;height:40px;border:1px solid #bfc8bb;border-radius:7px;background:transparent;font-size:14px;display:grid;place-items:center}
.icon-button:hover:not(:disabled){background:#e5e9dd}
.text-button{border:0;background:none;padding:0;font-weight:600;color:var(--green);text-decoration:underline;text-underline-offset:2px;font-size:inherit}
.subtle-link{border-color:transparent;padding-left:0;color:var(--green);text-decoration:underline;text-underline-offset:3px}

.play-area{display:grid;grid-template-columns:minmax(0,1fr) 340px;align-items:start;gap:28px;scroll-margin-top:16px}
.board-section{min-width:0;max-width:640px;width:100%;justify-self:center}
.turn-bar{display:flex;align-items:center;justify-content:space-between;gap:12px;padding:0 1px 14px}
.turn-player{display:flex;gap:12px;align-items:center;min-width:0}
.player-dot{width:12px;height:12px;border-radius:50%;flex-shrink:0;box-shadow:0 0 0 4px #e7e7db}
.player-dot.w{background:#fffdf3;border:1px solid #8c8a7c}
.player-dot.b{background:#26302c}
.turn-player strong{font-size:14px;font-weight:650;display:block}
.turn-player span:not(.player-dot){font-size:11px;color:var(--muted);display:block;margin-top:3px}
.turn-count{border:1px solid var(--line);padding:6px 9px;font-size:9px;letter-spacing:1.2px;border-radius:4px;white-space:nowrap}

.board-frame{background:var(--frame-bg);border:1px solid var(--frame-line);transition:background .3s;border-radius:10px;padding:11px 11px 4px 3px;box-shadow:0 8px 25px #283d3510}
.board-surround{display:grid;grid-template-columns:19px 1fr;grid-template-rows:1fr 21px}
.rank-labels{grid-column:1;grid-row:1;display:grid;grid-template-rows:repeat(8,1fr);font-size:10px;color:var(--frame-ink);align-items:center;justify-items:center}
.file-labels{grid-column:2;grid-row:2;display:grid;grid-template-columns:repeat(8,1fr);font-size:10px;color:var(--frame-ink);align-items:center;justify-items:center}
.board-wrap{grid-column:2;grid-row:1;position:relative}
.board{display:grid;grid-template-columns:repeat(8,minmax(0,1fr));aspect-ratio:1;box-shadow:0 0 0 1px #b0bba5;border-radius:3px;overflow:hidden}
.square{position:relative;border:0;border-radius:0;padding:0;aspect-ratio:1;min-width:0;display:grid;place-items:center;background:var(--sq-light)}
.square.dark{background:var(--sq-dark)}
.square.last-move{background:var(--sq-last-light)}
.square.dark.last-move{background:var(--sq-last-dark)}
.square.selected{background:var(--sq-sel-light)}
.square.dark.selected{background:var(--sq-sel-dark)}
.square.marked{box-shadow:inset 0 0 0 4px #c2954799}
.square.in-check{background:radial-gradient(circle,#e0573fcc 0,#e0573f55 45%,transparent 72%)}
.square:hover{filter:brightness(1.04)}
.square:focus-visible{outline:3px solid #30594b;outline-offset:-3px;z-index:3}
.square.legal::after{content:"";width:28%;aspect-ratio:1;border-radius:50%;background:var(--dot);position:absolute;pointer-events:none}
.square.capture::after{content:"";position:absolute;inset:4%;border-radius:50%;border:4px solid var(--dot);pointer-events:none}

.piece{position:relative;font-family:"Segoe UI Symbol","Apple Symbols","Arial Unicode MS","DejaVu Sans",serif;font-size:clamp(28px,6.6vw,58px);line-height:1;pointer-events:none;user-select:none;font-variant-emoji:text}
.piece::before{content:attr(data-fill);position:absolute;inset:0}
.piece.w{color:var(--pw-line)}
.piece.w::before{color:var(--pw-fill)}
.piece.b{color:var(--pb-line)}
.piece.b::before{color:var(--pb-fill)}
.piece{text-shadow:0 2px 2px #1f352f33}

.arrows{position:absolute;inset:0;width:100%;height:100%;pointer-events:none;overflow:visible}
.arrow{stroke-width:15;stroke-linecap:round;opacity:.78}
.arrow.idea{stroke:var(--arrow)}
.arrow.hint{stroke:#2f7a52}

.controls{display:flex;gap:8px;justify-content:center;padding:14px 0 4px}
.next-button{min-width:150px}

.sidebar{display:flex;flex-direction:column;gap:14px;min-width:0}
.mode-tabs{display:grid;grid-template-columns:1fr 1fr;background:#e3e5d9;border-radius:9px;padding:4px;gap:4px}
.mode-tab{border:0;border-radius:6px;background:transparent;padding:9px;font-size:13px;font-weight:650;color:var(--muted)}
.mode-tab.active{background:var(--paper);color:var(--ink);box-shadow:0 1px 3px #283d3520}
.line-picker{display:block}
.line-picker select{width:100%;min-height:40px;border:1px solid #bfc8bb;border-radius:7px;background:var(--paper);padding:8px 10px;font-size:13px}

.panel{background:var(--paper);border:1px solid var(--line);border-radius:9px;padding:18px}
.panel-heading{display:flex;align-items:baseline;justify-content:space-between;gap:8px;margin-bottom:12px;flex-wrap:wrap}
.panel h2{font-size:18px;margin:0}
.micro-label{font-size:9px;letter-spacing:1.4px;font-weight:600;color:var(--muted)}

.coach{min-height:180px}
.coach-title{font-size:28px;margin:0 0 8px}
.coach-title.good{color:var(--good)}
.coach-text{font-size:14px;line-height:1.65;margin:0}
.feedback{font-size:13px;line-height:1.55;margin:12px 0 0;padding:10px 12px;border-radius:7px;border-left:3px solid}
.feedback.info{background:#eef0e6;border-color:#9baa8c}
.feedback.bad{background:#f7e9e3;border-color:var(--danger);color:#6f2f1f}
.feedback.branch{background:#f5eedb;border-color:var(--gold)}
.feedback.hint{background:#e6f1ea;border-color:var(--good)}
.feedback.done{background:#f5eedb;border-color:var(--gold)}
.feedback.mastered{background:#e2f0e6;border-color:var(--good);color:#1f5238;font-weight:600}
.coach-actions{display:flex;flex-wrap:wrap;gap:8px;margin-top:14px}

.branch-list{display:flex;flex-direction:column;gap:6px}
.branch{display:flex;align-items:baseline;gap:10px;text-align:left;border:1px solid var(--line);background:#fff;border-radius:7px;padding:9px 11px;font-size:12px}
.branch strong{font-size:14px;min-width:62px}
.branch span{color:var(--muted)}
.branch.current{border-color:var(--green);box-shadow:inset 3px 0 0 var(--green)}
.branch:hover{background:#f0f2e8}
.branches p{margin:0 0 10px}
.alt-note{font-size:12px}

.move-list{list-style:none;margin:0;padding:0;display:grid;grid-template-columns:1fr 1fr;gap:2px 10px;max-height:240px;overflow:auto}
.move-row{display:grid;grid-template-columns:28px 1fr 1fr;align-items:center}
.move-no{font-size:11px;color:var(--muted)}
.move{border:0;background:none;text-align:left;padding:4px 6px;border-radius:4px;font-size:13px;font-weight:550}
.move:hover:not(:disabled){background:#e5e9dd}
.move:disabled{opacity:1;cursor:default}
.move.current{background:var(--green);color:#fff}

.lower-area{display:grid;grid-template-columns:minmax(0,1.2fr) minmax(0,1fr);gap:28px;margin-top:32px;align-items:start}
.line-cards{display:flex;flex-direction:column;gap:18px}
.family{display:grid;grid-template-columns:repeat(auto-fill,minmax(220px,1fr));gap:10px}
.family>.eyebrow{grid-column:1/-1;margin:0}
.line-card{border:1px solid var(--line);border-radius:8px;padding:14px;background:#fff;display:flex;flex-direction:column}
.line-card.active{border-color:var(--green);box-shadow:0 0 0 1px var(--green)}
.line-card-title{display:flex;justify-content:space-between;align-items:start;gap:8px}
.line-card h3{font-size:16px;margin:0}
.line-card p{margin:6px 0}
.badge{font-size:10px;font-weight:700;color:var(--good);background:#e2f0e6;border-radius:10px;padding:3px 8px;white-space:nowrap}
.ideas{margin:4px 0 12px;padding-left:16px;font-size:12px;line-height:1.55;color:#46524b;flex:1}
.card-actions{display:flex;gap:6px;flex-wrap:wrap}

.tree{font-size:13px;overflow-x:auto}
.tree-moves{display:flex;flex-wrap:wrap;gap:2px;align-items:center}
.tree-move{border:0;background:none;padding:3px 5px;border-radius:4px;font-weight:550}
.tree-move:hover{background:#e5e9dd}
.tree-move.on-path{color:var(--green);font-weight:700}
.tree-move.current{background:var(--green);color:#fff}
.tree-tag{font-size:10px;font-weight:700;letter-spacing:.4px;color:#7a6331;background:#f5eedb;border-radius:10px;padding:3px 8px;margin-left:4px}
.tree-tag.done{color:var(--good);background:#e2f0e6}
.tree-branches{list-style:none;margin:4px 0 4px 8px;padding:0 0 0 12px;border-left:2px solid var(--line)}
.tree-branches>li{margin:6px 0}

.page-footer{display:flex;justify-content:space-between;gap:16px;font-size:11px;color:var(--muted);border-top:1px solid var(--line);margin-top:36px;padding:22px 0 36px}

@media(max-width:980px){
  .play-area{grid-template-columns:1fr}
  .lower-area{grid-template-columns:1fr}
  .sidebar{max-width:640px;width:100%;justify-self:center}
}
@media(max-width:680px){
  .page-shell{padding:0 16px}
  .site-header{min-height:72px}
  .brand{font-size:20px}
  .brand small{display:none}
  .intro{display:block;margin:22px 0 18px}
  .intro>p{text-align:left;margin-top:10px}
  .board-frame{padding:6px 6px 2px 1px}
  .board-surround{grid-template-columns:14px 1fr;grid-template-rows:1fr 16px}
  .coach-title{font-size:24px}
  .page-footer{flex-direction:column}
}
@media(prefers-reduced-motion:reduce){*{transition:none!important;scroll-behavior:auto!important}}
.your-move{display:grid;gap:3px;font-size:12px;line-height:1.5;color:var(--muted);padding:0 0 12px;margin-bottom:12px;border-bottom:1px solid var(--line)}
.your-move strong{color:var(--good);font-size:13px}
.square.moving{z-index:5}
.square .piece{z-index:1}
.piece.ghost{position:absolute;z-index:0}
.square.moving{z-index:5}
.square .piece{z-index:1}
.piece.ghost{position:absolute;z-index:0}
.header-actions{display:flex;gap:10px;align-items:center}
.sound-toggle{min-height:32px;padding:6px 12px;border-radius:20px;font-size:11px}
.sound-toggle.off{color:var(--muted);border-style:dashed}
.sound-toggle,.progress-pill,.brand{white-space:nowrap}
.sound-toggle{gap:6px}
@media(max-width:680px){.sound-label{display:none}.sound-toggle{width:34px;padding:0}.brand{font-size:18px}.brand-mark{width:38px;height:38px;font-size:26px}}

/* Playful feedback */
.turn-badges{display:flex;gap:8px;align-items:center}
.streak{font-size:11px;font-weight:700;color:#8a4b14;background:#fbe6c8;border:1px solid #f0c48a;border-radius:20px;padding:5px 10px;white-space:nowrap}
.square.selected .piece{animation:lift .32s cubic-bezier(.3,1.7,.5,1) forwards}
@keyframes lift{0%{transform:none}100%{transform:translateY(-7%) scale(1.12)}}
.square.legal::after,.square.capture::after{animation:dot-in .2s cubic-bezier(.3,1.6,.5,1) backwards}
@keyframes dot-in{from{transform:scale(0);opacity:0}}
.fresh .arrow{animation:arrow-in .4s ease-out .22s backwards}
@keyframes arrow-in{from{opacity:0}}
.ripple{position:absolute;inset:6%;border-radius:50%;border:4px solid #2f7a52;pointer-events:none;z-index:2}
.cheer{position:absolute;left:50%;top:0;z-index:6;white-space:nowrap;pointer-events:none;font:700 15px/1 Georgia,serif;color:#fff;background:#2f7a52;border-radius:20px;padding:6px 11px;box-shadow:0 4px 12px #1f352f40}
.board{overflow:visible}
.board-wrap{overflow:visible}
.confetti{position:fixed;inset:0;width:100vw;height:100vh;pointer-events:none;z-index:50}
.feedback.mastered{animation:glow 1.6s ease-out .5s backwards}
@keyframes glow{from{box-shadow:0 0 0 0 #2f7a5266}to{box-shadow:0 0 0 14px #2f7a5200}}
.mode-tab,.branch,.line-card,.tree-move,.button{transition:transform .15s cubic-bezier(.3,1.6,.5,1),background .15s}
.button:active:not(:disabled),.branch:active,.tree-move:active{transform:scale(.95)}
.line-card:hover{transform:translateY(-2px)}
@media(prefers-reduced-motion:reduce){.square.selected .piece,.square.legal::after,.square.capture::after,.fresh .arrow,.feedback.mastered{animation:none}}

/* Theme picker */
.theme-dialog{border:1px solid var(--line);border-radius:14px;background:var(--paper);color:var(--ink);padding:22px;width:min(520px,calc(100vw - 32px));box-shadow:0 20px 60px #1f352f40}
.theme-dialog::backdrop{background:#1f352f55}
.theme-dialog h2{font-size:24px;margin:0 0 4px}
.dialog-heading{display:flex;justify-content:space-between;align-items:start;gap:12px}
.swatches{display:grid;grid-template-columns:repeat(auto-fill,minmax(78px,1fr));gap:10px;margin:8px 0 20px}
.swatch{border:2px solid transparent;border-radius:10px;background:#fff;padding:8px;display:grid;gap:6px;justify-items:center;font-size:11px;font-weight:650;box-shadow:0 0 0 1px var(--line)}
.swatch:hover{transform:translateY(-2px)}
.swatch[aria-pressed="true"]{border-color:var(--green)}
.mini-board{display:grid;grid-template-columns:repeat(2,26px);grid-template-rows:repeat(2,26px);border-radius:4px;overflow:hidden;box-shadow:0 0 0 3px var(--frame-bg)}
.mini-board span{display:grid;place-items:center;font-size:20px;line-height:1}
.mini-board .l{background:var(--sq-light)}
.mini-board .d{background:var(--sq-dark)}
.mini-board .l:last-child{background:var(--sq-last-light)}
.mini-pieces{display:flex;gap:2px;font-size:30px;line-height:1;padding:4px 0}
.mini-pieces .piece{font-size:30px}

/* Drill and either-side practice */
.mode-tabs{grid-template-columns:repeat(3,1fr)}
.tab-badge{display:inline-grid;place-items:center;min-width:18px;height:18px;padding:0 5px;margin-left:4px;border-radius:9px;background:var(--danger);color:#fff;font-size:10px;font-weight:700;vertical-align:1px}
.side-toggle{display:flex;align-items:center;gap:6px;margin-bottom:12px}
.side-toggle .eyebrow{margin:0 4px 0 0}
.side-choice{border:1px solid #bfc8bb;background:#fff;border-radius:20px;padding:4px 12px;font-size:12px;font-weight:600}
.side-choice.active{background:var(--ink);border-color:var(--ink);color:#fff}
.badges{display:flex;gap:4px;flex-wrap:wrap;justify-content:flex-end}
.badge.due{color:#8a4b14;background:#fbe6c8}
.feedback.solved{background:#e2f0e6;border-color:var(--good);color:#1f5238}
.drill-results{list-style:none;margin:12px 0 0;padding:0;display:grid;gap:4px;font-size:13px}
.drill-results button{width:100%;text-align:left;display:grid;grid-template-columns:20px 1fr auto;gap:6px;align-items:center;padding:6px 8px;border-radius:6px;background:#fff;border:1px solid var(--line);font-size:13px}
.drill-results button:hover{background:#f0f2e8}
.drill-results .clean .mark{color:var(--good);font-weight:700}
.drill-results .missed .mark{color:var(--danger);font-weight:700}
.drill-results small{color:var(--muted)}

/* Opening switcher */
.opening-tabs{display:flex;gap:6px;flex-wrap:wrap;margin-bottom:14px}
.opening-tab{border:1px solid #bfc8bb;background:transparent;border-radius:20px;padding:7px 14px;font-size:12px;font-weight:650;color:var(--muted)}
.opening-tab:hover{background:#e5e9dd}
.opening-tab.active{background:var(--green);border-color:var(--green);color:#fff}
.opening-tabs{gap:8px 18px}
.opening-group{display:flex;gap:6px;flex-wrap:wrap;align-items:center}
.opening-group-label{font-size:11px;font-weight:700;color:var(--muted);margin-right:2px}