:root{color-scheme:dark;--bg:#171816;--ink:#f6f5ef;--muted:#bbbdb3;--green:#a4e26b;--line:#ffffff20}*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--ink);font-family:ui-rounded,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;line-height:1.55}header,main,footer{width:min(1120px,calc(100% - 48px));margin:auto}header{display:flex;align-items:center;justify-content:space-between;padding:24px 0;gap:20px}.brand{font-size:15px;letter-spacing:.13em;font-weight:800;text-decoration:none;color:var(--ink)}a{color:var(--green)}button,.app{font:inherit;font-weight:700;border-radius:13px;border:1px solid var(--line);padding:12px 17px;background:#ffffff09;color:var(--ink);cursor:pointer;text-decoration:none;display:inline-flex;align-items:center;justify-content:center;min-height:48px}button:hover,.app:hover{background:#ffffff15}button:focus-visible,a:focus-visible{outline:3px solid var(--green);outline-offset:5px}.app,.primary{background:var(--green);color:#192114;border-color:transparent}.app:hover,.primary:hover{background:#b8ed8c}.small{font-size:13px;min-height:42px;padding:8px 14px}.intro{padding:52px 0 44px}.eyebrow{font-size:11px;letter-spacing:.15em;font-weight:800;color:var(--green)}h1{font-size:clamp(58px,9vw,104px);letter-spacing:-.065em;line-height:.95;margin:20px 0 24px}h2{font-size:clamp(30px,4vw,44px);line-height:1.12;letter-spacing:-.04em;margin:12px 0 20px}.intro p{font-size:20px;color:var(--muted);margin:0}.practice{display:grid;grid-template-columns:.85fr 1.15fr;gap:60px;border:1px solid var(--line);border-radius:28px;padding:40px;background:#ffffff03;align-items:start;scroll-margin-top:24px}.lesson{padding-top:8px}.progress{display:flex;gap:7px;margin-bottom:26px}.progress span{height:5px;width:37px;border-radius:4px;background:#ffffff26}.progress .done{background:var(--green)}#instruction{color:var(--muted);font-size:17px;max-width:330px}.rule{border-left:2px solid var(--green);padding-left:16px;margin:28px 0}.rule>span{font-size:10px;font-weight:800;letter-spacing:.13em;color:var(--green)}.rule p{font-size:15px;margin:8px 0;color:var(--muted)}.feedback{font-size:16px;min-height:76px}.feedback.success{color:var(--green)}.path{font-variant-numeric:tabular-nums;color:var(--green);font-size:18px;min-height:28px;font-weight:700}.actions{display:flex;gap:9px;flex-wrap:wrap}.actions button{font-size:13px;padding:10px 13px}.board-label{display:flex;justify-content:space-between;gap:8px;color:var(--muted);font-size:10px;font-weight:800;letter-spacing:.13em;padding-bottom:12px}#board{border:8px solid #a28e6c;border-radius:10px;overflow:hidden;aspect-ratio:1;background:#e4dcc9;box-shadow:0 22px 60px #0005}.board-row{display:grid;grid-template-columns:repeat(8,1fr);height:12.5%}.square{border:0;border-radius:0;background:#e7dfcc;min-height:0;padding:0;position:relative;display:flex;align-items:center;justify-content:center;color:#1a251f;touch-action:manipulation;aspect-ratio:1}.square.dark{background:#5b715e}.square:hover{background:#ddd2b7}.square.dark:hover{background:#6a826d}.square:focus-visible{z-index:2;outline:3px solid #fff;outline-offset:-4px}.square.selected{box-shadow:inset 0 0 0 4px #e2fe90}.square.last{box-shadow:inset 0 0 0 3px #e2fe90a6}.coord{position:absolute;left:3px;top:0;font-size:10px;line-height:1.5;opacity:.9;color:#182018}.dark .coord{color:#fff}.piece{width:75%;height:75%;border-radius:50%;display:flex;align-items:center;justify-content:center;line-height:1;font-size:clamp(15px,3vw,29px);font-weight:900;box-shadow:0 4px 0 #0006,0 6px 8px #0003,inset 0 0 0 3px #0002;pointer-events:none}.piece.light{background:#f3eddf;color:#2a3027;border:2px solid #fff8}.piece.black{background:#252c27;color:#e5d59f;border:2px solid #414a42}.legend{display:flex;justify-content:center;gap:24px;font-size:12px;color:var(--muted);padding-top:17px}.legend span{display:flex;align-items:center;gap:7px}.white-dot,.black-dot{width:11px;height:11px;border-radius:50%;background:#f3eddf;border:1px solid #ffffff50}.black-dot{background:#252c27}.rules{padding:84px 0 60px}.rules>h2{font-size:32px}.rule-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:30px}.rule-grid h3{font-size:18px;margin:12px 0}.rule-grid p,.source,.cta p{color:var(--muted);font-size:15px}.source{font-size:12px;margin-top:30px;max-width:850px}.cta{border-top:1px solid var(--line);padding:36px 0;display:flex;align-items:center;gap:40px;justify-content:space-between}.cta h2{font-size:29px;margin:0 0 10px}.cta p{max-width:550px}.cta .app{flex-shrink:0;font-size:14px}.finish{text-align:center;margin-top:35px;padding:45px;border:1px solid #a4e26b50;border-radius:25px;background:#a4e26b09}.finish p{max-width:550px;margin:20px auto;color:var(--muted)}.finish h2{font-size:44px}.finish .limits{font-size:13px}.finish button{font-size:13px}.notice{padding:20px;border:1px solid var(--line)}footer{display:flex;justify-content:space-between;gap:20px;border-top:1px solid var(--line);padding:24px 0 42px;color:var(--muted);font-size:12px}footer div{display:flex;gap:20px}.skip{position:absolute;top:-100px;left:10px;padding:10px;background:#171816;z-index:100}.skip:focus{top:10px}[hidden]{display:none!important}@media(max-width:820px){.practice{grid-template-columns:1fr;gap:25px;padding:28px}.board-wrap{grid-row:2}.feedback{min-height:42px}.rule{margin:20px 0}.path{margin:10px 0}.progress{margin-bottom:20px}.lesson>h2{margin-bottom:14px}.rule-grid{grid-template-columns:1fr;gap:9px}.rules{padding-top:55px}.cta{display:block}.cta .app{margin-top:15px}.coord{font-size:9px}.piece{font-size:30px}#instruction{max-width:none}.intro{padding-top:36px}.intro p{font-size:18px}}@media(max-width:440px){header,main,footer{width:calc(100% - 32px)}header{gap:10px}.brand{font-size:12px}.small{font-size:11px;padding:8px 10px}.practice{padding:20px 15px;border-radius:20px}.intro{padding:30px 0}h1{font-size:62px}.board-label{font-size:9px}.legend{gap:15px;font-size:11px}#board{border-width:6px}.coord{font-size:9px}.piece{font-size:22px}.finish{padding:30px 18px}.finish h2{font-size:34px}.feedback{font-size:15px}footer{font-size:11px}}@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important}}
@media(max-width:820px){.practice{display:flex;flex-direction:column;gap:0}.lesson{display:contents}.progress{order:1;margin:0 0 15px}#lesson-count{order:2;margin:0 0 8px}#lesson-title{order:3;margin:0 0 12px}#instruction{order:4;margin:0 0 22px}.board-wrap{order:5;width:100%}.rule{order:6}.feedback{order:7;width:100%}.path{order:8}.actions{order:9;gap:8px}.intro{padding:22px 0 28px}.intro h1{margin:16px 0 18px}.intro p{font-size:17px}.board-label{padding-bottom:10px}}