:root{--bg:#f5f3ee;--surface:#fffdfa;--surface-2:#eee9df;--ink:#1e2430;--muted:#6d7280;--line:#d8d1c5;--brand:#5f4bb6;--brand-2:#d59b2d;--good:#23845b;--bad:#c63d45;--shadow:0 18px 45px rgba(33,29,23,.12);--radius:18px;--board-light:#f0d9b5;--board-dark:#8b6f47;--max:1240px;font-family:Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;color-scheme:light dark}
@media(prefers-color-scheme:dark){:root{--bg:#15171c;--surface:#20232b;--surface-2:#2a2e38;--ink:#f5f4f0;--muted:#aeb4c1;--line:#3b404b;--shadow:0 18px 45px rgba(0,0,0,.3)}}
*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:var(--bg);color:var(--ink);line-height:1.55}a{color:var(--brand)}button,input,select,textarea{font:inherit;color:inherit}button{cursor:pointer}img,svg{max-width:100%}.container{width:min(var(--max),calc(100% - 32px));margin:auto}.site-header{position:sticky;top:0;z-index:50;background:color-mix(in srgb,var(--surface) 92%,transparent);backdrop-filter:blur(12px);border-bottom:1px solid var(--line)}.header-inner{height:70px;display:flex;align-items:center;gap:20px}.brand{display:flex;align-items:center;gap:11px;font-weight:850;text-decoration:none;color:var(--ink);font-size:1.12rem}.brand-mark{width:38px;height:38px;border-radius:12px;background:linear-gradient(145deg,var(--brand),#8d7ce0);display:grid;place-items:center;color:white;font-size:22px;box-shadow:0 8px 22px rgba(95,75,182,.28)}.main-nav{display:flex;gap:18px;margin-left:auto}.main-nav a{text-decoration:none;color:var(--ink);font-weight:650;font-size:.94rem}.lang-switch{border:1px solid var(--line);border-radius:999px;padding:7px 12px;text-decoration:none;color:var(--ink);font-weight:750}.menu-toggle{display:none;margin-left:auto}.hero{padding:76px 0 48px;background:radial-gradient(circle at 82% 10%,rgba(95,75,182,.19),transparent 36%),radial-gradient(circle at 12% 82%,rgba(213,155,45,.14),transparent 32%)}.hero-grid{display:grid;grid-template-columns:1.05fr .95fr;gap:52px;align-items:center}.eyebrow{display:inline-flex;gap:8px;align-items:center;border:1px solid var(--line);background:var(--surface);padding:7px 12px;border-radius:999px;color:var(--muted);font-weight:700;font-size:.85rem}.hero h1{font-size:clamp(2.6rem,6vw,5.4rem);line-height:.94;letter-spacing:-.055em;margin:20px 0 24px;max-width:850px}.hero p{font-size:1.17rem;color:var(--muted);max-width:680px}.hero-actions{display:flex;flex-wrap:wrap;gap:12px;margin:28px 0}.btn,.hero-actions a{display:inline-flex;align-items:center;justify-content:center;border-radius:13px;padding:12px 18px;text-decoration:none;font-weight:780;border:1px solid var(--line);background:var(--surface);color:var(--ink)}.btn-primary,.hero-actions a:first-child{background:var(--brand);color:white;border-color:var(--brand);box-shadow:0 10px 25px rgba(95,75,182,.28)}.trust-line{display:flex;flex-wrap:wrap;gap:20px;color:var(--muted);font-size:.9rem}.hero-board{background:var(--surface);padding:18px;border-radius:28px;box-shadow:var(--shadow);transform:rotate(1deg);border:1px solid var(--line)}.mini-board{display:grid;grid-template-columns:repeat(8,1fr);aspect-ratio:1;border-radius:12px;overflow:hidden}.mini-board span{display:grid;place-items:center;font-size:clamp(20px,4vw,50px);line-height:1}.mini-board span:nth-child(16n+1),.mini-board span:nth-child(16n+3),.mini-board span:nth-child(16n+5),.mini-board span:nth-child(16n+7),.mini-board span:nth-child(16n+10),.mini-board span:nth-child(16n+12),.mini-board span:nth-child(16n+14),.mini-board span:nth-child(16n+16){background:var(--board-light)}.mini-board span{background:var(--board-dark)}.section{padding:72px 0}.section.alt{background:var(--surface-2)}.section h2{font-size:clamp(2rem,4vw,3.4rem);letter-spacing:-.035em;margin:0 0 12px}.lead{color:var(--muted);max-width:760px;font-size:1.08rem}.card-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:20px;margin-top:34px}.tool-card,.guide-card,.info-card{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:24px;box-shadow:0 8px 24px rgba(25,22,18,.06);text-decoration:none;color:var(--ink);transition:.2s transform,.2s box-shadow}.tool-card:hover,.guide-card:hover{transform:translateY(-4px);box-shadow:var(--shadow)}.tool-icon{width:48px;height:48px;border-radius:14px;display:grid;place-items:center;background:color-mix(in srgb,var(--brand) 12%,var(--surface));font-size:24px}.tool-card h3,.guide-card h3{margin:16px 0 8px;font-size:1.18rem}.tool-card p,.guide-card p{color:var(--muted);margin:0}.feature-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:18px;margin-top:30px}.feature{padding:21px;border-top:3px solid var(--brand);background:var(--surface);border-radius:0 0 var(--radius) var(--radius)}.faq{max-width:880px;margin-top:30px}.faq details{background:var(--surface);border:1px solid var(--line);border-radius:14px;padding:18px 20px;margin:10px 0}.faq summary{font-weight:780;cursor:pointer}.breadcrumbs{font-size:.88rem;color:var(--muted);padding:18px 0}.breadcrumbs a{color:inherit}.page-head{padding:38px 0 28px}.page-head h1{font-size:clamp(2.25rem,5vw,4.3rem);letter-spacing:-.045em;line-height:1;margin:12px 0}.page-head p{max-width:760px;color:var(--muted);font-size:1.08rem}.app-shell{width:min(1480px,calc(100% - 24px));margin:0 auto 60px}.chess-toolbar{display:flex;flex-wrap:wrap;gap:8px;padding:12px;background:var(--surface);border:1px solid var(--line);border-radius:16px 16px 0 0}.chess-toolbar button,.panel button{border:1px solid var(--line);background:var(--surface-2);border-radius:10px;padding:9px 12px;font-weight:720}.chess-toolbar button:hover,.panel button:hover{border-color:var(--brand)}.panel button.primary,.panel .primary{background:var(--brand);color:#fff;border-color:var(--brand)}.chess-workspace{display:grid;grid-template-columns:minmax(230px,290px) minmax(420px,720px) minmax(250px,340px);gap:14px;align-items:start;background:color-mix(in srgb,var(--surface-2) 60%,transparent);border:1px solid var(--line);border-top:0;padding:14px;border-radius:0 0 18px 18px}.panel{background:var(--surface);border:1px solid var(--line);border-radius:14px;padding:16px;max-height:780px;overflow:auto}.panel h2{margin:0 0 16px;font-size:1.25rem}.panel label{display:grid;gap:6px;margin:12px 0;font-size:.9rem;font-weight:700}.panel input,.panel select,.panel textarea{width:100%;border:1px solid var(--line);background:var(--bg);border-radius:9px;padding:9px}.panel textarea{resize:vertical}.panel button{width:100%;margin:5px 0}.board-area{min-width:0}.board-wrap{position:relative;width:min(100%,720px);margin:auto;box-shadow:var(--shadow);border-radius:8px;overflow:hidden}.chessboard{display:grid;grid-template-columns:repeat(8,1fr);aspect-ratio:1;background:#222}.square{position:relative;border:0;padding:0;display:grid;place-items:center;min-width:0;aspect-ratio:1}.square.light{background:var(--board-light)}.square.dark{background:var(--board-dark)}.square.selected{box-shadow:inset 0 0 0 6px #f7c948}.square:focus-visible{z-index:2;outline:4px solid var(--brand);outline-offset:-4px}.piece{font-family:"DejaVu Sans","Segoe UI Symbol",Arial,sans-serif;font-size:clamp(34px,7vw,72px);line-height:1;text-shadow:0 1px 1px rgba(0,0,0,.15);user-select:none}.coord{position:absolute;font-size:10px;font-weight:850;opacity:.72}.coord.file{bottom:2px;right:4px}.coord.rank{top:2px;left:4px}.board-overlay{position:absolute;inset:0;width:100%;height:100%;pointer-events:none}.board-status{margin:12px auto 0;width:min(100%,720px);background:var(--surface);border:1px solid var(--line);border-radius:12px;padding:11px 15px;font-weight:800;text-align:center}.privacy-note{text-align:center;color:var(--muted);font-size:.82rem}.tabs{display:flex;border-bottom:1px solid var(--line);margin:-4px -4px 12px}.tabs button{border:0;background:transparent;padding:10px 8px;border-radius:0;margin:0;font-size:.84rem}.tabs button.active{color:var(--brand);box-shadow:inset 0 -3px var(--brand)}.tab-content{display:none}.tab-content.active{display:block}.move-tree{max-height:500px;overflow:auto}.move-node{padding-left:calc(var(--level)*12px);display:flex;align-items:center;gap:5px}.move-node button{width:auto;min-width:66px;text-align:left;border:0;background:transparent;padding:5px 7px;margin:1px;font-weight:650}.move-node.current button{background:color-mix(in srgb,var(--brand) 18%,transparent);color:var(--brand)}.move-node.variation{border-left:2px solid var(--line)}.move-no{color:var(--muted);font-size:.75rem;margin-right:5px}.comment-dot{font-size:8px;color:var(--brand)}.engine-line{border-bottom:1px solid var(--line);padding:10px 0}.engine-line strong{font-size:1.15rem;color:var(--brand);margin-right:8px}.engine-line span{color:var(--muted);font-size:.8rem}.engine-line p{margin:5px 0;font-size:.87rem}.eval-graph svg{width:100%;margin-top:12px;background:var(--surface-2);border-radius:10px}.spinner{width:32px;height:32px;border:4px solid var(--line);border-top-color:var(--brand);border-radius:50%;animation:spin .8s linear infinite;margin:28px auto}@keyframes spin{to{transform:rotate(360deg)}}.piece-palette{display:grid;grid-template-columns:repeat(4,1fr);gap:6px}.piece-palette button{font-size:30px;padding:6px}.piece-palette button.active{outline:3px solid var(--brand)}.coordinate-target{font-size:4rem;font-weight:900;text-align:center;background:var(--surface-2);border-radius:14px;padding:15px}.chess-clock{min-height:660px;display:grid;grid-template-rows:1fr auto 1fr;gap:12px}.clock-side{border:0;border-radius:22px;display:flex;align-items:center;justify-content:space-between;padding:30px;font-size:1.2rem;font-weight:800}.clock-side strong{font-size:clamp(3rem,9vw,7rem);font-variant-numeric:tabular-nums}.clock-side.black{background:#282b33;color:#fff;transform:rotate(180deg)}.clock-side.white{background:#f2eee5;color:#17191f}.clock-side.active{box-shadow:inset 0 0 0 8px var(--brand-2)}.clock-controls{display:flex;flex-wrap:wrap;align-items:end;justify-content:center;gap:8px}.clock-controls label{display:grid;font-size:.75rem}.clock-controls input{width:76px;padding:8px}.clock-controls button{padding:10px 14px;border-radius:10px;border:1px solid var(--line)}.library-item{border-bottom:1px solid var(--line);padding:12px 0}.library-item strong,.library-item small{display:block}.library-item small{color:var(--muted);margin:4px 0}.library-item div{display:flex;gap:4px}.library-item button{width:auto;font-size:.75rem;padding:6px 8px}.toast{position:fixed;left:50%;bottom:26px;transform:translate(-50%,20px);background:#16181e;color:white;border-radius:999px;padding:11px 18px;opacity:0;pointer-events:none;transition:.25s;z-index:100}.toast.show{opacity:1;transform:translate(-50%,0)}.ad-slot{min-height:120px;display:grid;place-items:center;color:var(--muted);font-size:.8rem;border:1px dashed var(--line);border-radius:14px;margin:30px 0}.article-layout{display:grid;grid-template-columns:minmax(0,760px) 280px;gap:54px}.article-content h2{margin-top:42px;font-size:1.7rem}.article-content h3{margin-top:28px}.article-content p,.article-content li{color:color-mix(in srgb,var(--ink) 85%,var(--muted))}.article-content .callout{background:var(--surface);border-left:4px solid var(--brand);border-radius:0 12px 12px 0;padding:18px 20px;margin:24px 0}.toc{position:sticky;top:90px;background:var(--surface);border:1px solid var(--line);border-radius:14px;padding:18px}.toc a{display:block;color:var(--muted);text-decoration:none;padding:5px 0}.site-footer{background:#101217;color:#dfe2e8;padding:54px 0 28px}.footer-grid{display:grid;grid-template-columns:1.2fr 2fr;gap:50px}.footer-links{display:grid;grid-template-columns:repeat(3,1fr);gap:12px}.footer-links a{color:#dfe2e8;text-decoration:none}.footer-bottom{margin-top:34px;padding-top:20px;border-top:1px solid #333844;color:#8f96a3;font-size:.85rem}.legal{max-width:850px}.legal h2{margin-top:36px}.notice{background:color-mix(in srgb,var(--brand) 10%,var(--surface));border:1px solid color-mix(in srgb,var(--brand) 30%,var(--line));padding:16px;border-radius:12px}.error-page{text-align:center;padding:100px 20px}.error-page strong{font-size:7rem;color:var(--brand)}
@media(max-width:1100px){.chess-workspace{grid-template-columns:230px minmax(360px,1fr)}.side-panel{grid-column:1/-1;max-height:none}.side-panel .tabs{max-width:600px}.card-grid{grid-template-columns:repeat(2,1fr)}.feature-grid{grid-template-columns:repeat(2,1fr)}}
@media(max-width:780px){.main-nav{display:none}.menu-toggle{display:block}.hero{padding-top:44px}.hero-grid,.article-layout,.footer-grid{grid-template-columns:1fr}.hero-board{max-width:520px}.card-grid,.feature-grid{grid-template-columns:1fr}.chess-toolbar{border-radius:12px 12px 0 0}.chess-workspace{display:flex;flex-direction:column;padding:8px}.tool-panel{order:2;width:100%;max-height:none}.board-area{order:1;width:100%}.side-panel{order:3;width:100%}.piece{font-size:clamp(28px,11vw,58px)}.app-shell{width:calc(100% - 8px)}.page-head{padding-top:24px}.article-layout .toc{position:static}.footer-links{grid-template-columns:1fr 1fr}.clock-side{padding:18px}.chess-clock{min-height:70vh}}
@media print{.site-header,.site-footer,.breadcrumbs,.page-head,.chess-toolbar,.tool-panel,.side-panel,.privacy-note,.ad-slot{display:none!important}.app-shell{width:100%;margin:0}.chess-workspace{display:block;border:0;padding:0}.board-wrap{width:180mm;box-shadow:none}.board-status{display:none}}