:root{--bg:#050505;--panel:#101010;--panel-2:#151515;--line:rgba(255,255,255,.1);--text:#f5f5f5;--muted:#a2a2a2;--green:#10a37f;--light:#eeeed2;--dark:#789453}
*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:radial-gradient(circle at 50% -20%,rgba(16,163,127,.17),transparent 38%),var(--bg);color:var(--text);font-family:Inter,system-ui,-apple-system,Segoe UI,sans-serif;line-height:1.55}a{color:inherit;text-decoration:none}.wrap{width:min(1100px,calc(100% - 40px));margin:auto}nav{height:68px;border-bottom:1px solid var(--line);background:rgba(5,5,5,.88);backdrop-filter:blur(18px);position:sticky;top:0;z-index:10}.nav-in{height:100%;display:flex;align-items:center;justify-content:space-between;gap:18px}.brand{font-weight:750;letter-spacing:-.02em}.nav-links{display:flex;gap:18px;align-items:center;color:var(--muted);font-size:14px}.btn,.choice,.line-button{border:0;border-radius:999px;padding:11px 17px;font:inherit;font-weight:650;cursor:pointer;transition:transform .15s,background .15s,border-color .15s}.btn:hover,.choice:hover,.line-button:hover{transform:translateY(-1px)}.btn{background:var(--green);color:#fff}.btn.ghost{background:transparent;border:1px solid var(--line);color:var(--text)}.hero{padding:72px 0 42px;text-align:center}.eyebrow{color:var(--green);font-size:12px;font-weight:750;letter-spacing:.11em;text-transform:uppercase}.hero h1{font-size:clamp(36px,6vw,62px);line-height:1.03;letter-spacing:-.055em;margin:14px auto;max-width:780px}.hero p{max-width:640px;color:var(--muted);margin:0 auto}.tool-shell{display:grid;grid-template-columns:minmax(260px,420px) 1fr;gap:26px;align-items:start;padding-bottom:66px}.board-card,.challenge-card,.info-card{background:linear-gradient(145deg,rgba(255,255,255,.055),rgba(255,255,255,.02));border:1px solid var(--line);border-radius:22px}.board-card{padding:16px;position:sticky;top:88px}.board{display:grid;grid-template-columns:repeat(8,minmax(0,1fr));grid-template-rows:repeat(8,minmax(0,1fr));width:100%;aspect-ratio:1;background:var(--light);border:0;overflow:hidden;border-radius:10px;box-shadow:0 10px 26px rgba(0,0,0,.22)}.square{display:grid;place-items:center;position:relative;line-height:1;min-width:0;min-height:0}.square.light{background:var(--light)}.square.dark{background:var(--dark)}.coord{display:none}.piece{display:block;width:92%;height:92%;object-fit:contain;pointer-events:none;user-select:none;filter:drop-shadow(0 1px 1px rgba(0,0,0,.16))}.piece.white{filter:drop-shadow(0 1px 1px rgba(0,0,0,.22))}.board-note{display:flex;justify-content:space-between;gap:8px;color:var(--muted);font-size:12px;padding:12px 4px 0}.challenge-card{padding:30px}.challenge-card h2{font-size:clamp(26px,4vw,38px);letter-spacing:-.04em;line-height:1.08;margin:8px 0 12px}.meta{display:flex;justify-content:space-between;gap:12px;color:var(--muted);font-size:13px}.progress{height:7px;background:#242424;border-radius:99px;overflow:hidden;margin:20px 0}.progress > i{display:block;height:100%;background:linear-gradient(90deg,var(--green),#49c99f);border-radius:inherit;transition:width .25s}.choices{display:grid;gap:10px;margin-top:22px}.choice{background:#181818;border:1px solid var(--line);color:var(--text);text-align:left}.choice.correct{background:rgba(16,163,127,.22);border-color:var(--green)}.choice.wrong{background:rgba(220,80,80,.18);border-color:#df6666}.feedback{min-height:48px;margin:18px 0 8px;color:var(--muted)}.feedback.good{color:#80e2bf}.feedback.bad{color:#f3abab}.next-row{display:flex;gap:10px;align-items:center;flex-wrap:wrap;margin-top:14px}.line-select{display:flex;gap:9px;flex-wrap:wrap;margin:0 0 18px}.line-button{background:#171717;border:1px solid var(--line);color:var(--muted);font-size:13px;padding:9px 14px}.line-button.active{border-color:var(--green);background:rgba(16,163,127,.14);color:#fff}.info-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:14px;padding:12px 0 72px}.info-card{padding:20px}.info-card h3{margin:0 0 7px;font-size:16px}.info-card p{margin:0;color:var(--muted);font-size:14px}.streak{display:flex;gap:10px;align-items:center;background:rgba(16,163,127,.12);border:1px solid rgba(16,163,127,.35);border-radius:16px;padding:13px 15px;margin:16px 0}.streak b{font-size:22px;color:#93f0ce}.done{display:none;margin-top:18px;padding:14px;border-radius:13px;background:rgba(16,163,127,.12);color:#9bebce}.done.show{display:block}.footer{border-top:1px solid var(--line);padding:28px 0 40px;color:var(--muted);font-size:13px}.tool-links{display:flex;gap:12px;flex-wrap:wrap;margin-top:10px}.tool-links a{color:#d7d7d7}.tool-links a:hover{color:var(--green)}
.source-card{margin-top:14px;padding:13px 14px;border:1px solid rgba(16,163,127,.3);border-radius:14px;background:rgba(16,163,127,.07)}.source-kicker{display:block;color:#74dfbc;font-size:10px;font-weight:800;letter-spacing:.1em;text-transform:uppercase;margin-bottom:3px}.source-card strong{font-size:14px}.source-card p{margin:6px 0 8px;color:var(--muted);font-size:12px;line-height:1.4}.source-card a{color:#9bebce;font-size:12px;font-weight:700}.source-card a:hover{text-decoration:underline}
@media(max-width:760px){.nav-links{display:none}.hero{padding:54px 0 28px}.tool-shell{grid-template-columns:1fr}.board-card{position:relative;top:0}.challenge-card{padding:22px}.info-grid{grid-template-columns:1fr}.wrap{width:min(100% - 30px,1100px)}}