:root,:root[data-theme=night]{color-scheme:dark;--bg:#0b1220;--surface:#131c2e;--surface-2:#1b2740;--border:#36456b;--hover:#243352;--text:#f4f7fb;--text-strong:#ffffff;--text-muted:#c2cde2;--placeholder:#9fb0d0;--accent:#6db3ff;--accent-strong:#9ccbff;--accent-ink:#04122b;--success:#5ee0a0;--warning:#ffc857;--danger:#ff8a8a;--code-bg:#0a1322;--focus:#ffd166;--shadow:0 2px 16px rgba(0,0,0,0.5)}:root[data-theme=day]{color-scheme:light;--bg:#f5f8ff;--surface:#ffffff;--surface-2:#eef3fb;--border:#c4d0e6;--hover:#e2eaf7;--text:#0f1830;--text-strong:#06101f;--text-muted:#3a4a6b;--placeholder:#5a6b8c;--accent:#1763c7;--accent-strong:#0f4ea3;--accent-ink:#ffffff;--success:#137a4d;--warning:#9a6700;--danger:#b4232b;--code-bg:#f0f3fa;--focus:#b25e00;--shadow:0 2px 16px rgba(15,24,48,0.18)}@media 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auto;width:54px;height:70px;border-radius:8px;display:grid;place-items:center;font-weight:800;font-size:1.05rem;color:#fff;box-shadow:var(--shadow);letter-spacing:-.02em}.book-cover.python{background:linear-gradient(150deg,#2f9e6e,#5ee0a0)}.book-cover.cpp{background:linear-gradient(150deg,#1763c7,#6db3ff)}.book-cover.cuda{background:linear-gradient(150deg,#7c3aed,#c792ea)}.book-cover.csharp{background:linear-gradient(150deg,#5b2d8e,#9b6dd6)}.book-title{font-size:1.2rem;margin:0 0 4px;line-height:1.25}.book-meta{color:var(--text-muted);margin:0;font-size:.95rem}.chip-row{display:flex;gap:8px;flex-wrap:wrap;margin-top:8px}.chip{font-size:.78rem;font-weight:700;padding:3px 10px;border-radius:999px;border:1px solid var(--border);color:var(--text-muted)}.chip.accent{background:var(--accent);color:var(--accent-ink);border-color:var(--accent)}.book-progress{margin-top:14px}.book-progress .pct{margin:6px 0 0;font-weight:600;font-size:.92rem}.book-actions{display:flex;gap:10px;align-items:center;flex-wrap:wrap;margin-top:14px;padding-top:14px;border-top:1px solid var(--border)}.book-actions .spacer{flex:1 1 auto}.error{color:var(--danger)}.error,.ok{font-weight:600}.ok{color:var(--success)}.mono,code,pre{font-family:var(--font-mono)}pre{background:var(--code-bg);border:1px solid var(--border);border-radius:var(--radius);padding:14px;overflow:auto}.tablist{display:flex;flex-wrap:wrap;gap:4px;padding:4px;background:var(--surface-2);border:1px solid var(--border);border-radius:12px;margin-bottom:18px}.tab{min-height:40px;flex:1 1 auto;border:1px solid transparent;border-radius:9px;background:transparent;color:var(--text-muted);font-weight:700}.tab:hover:not(.active){background:var(--hover);border-color:transparent}.tab.active{color:var(--accent-ink);background:var(--accent);border-color:var(--accent);box-shadow:0 4px 12px color-mix(in srgb,var(--accent) 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pre{font-size:.95rem}.quiz-question{display:block;font-weight:700;font-size:1.05rem;line-height:1.4;color:var(--accent-strong);margin-bottom:10px}.quiz-num{color:var(--text-muted);font-weight:700;margin-right:4px}.quiz-option{width:100%;justify-content:flex-start;text-align:left;margin-bottom:8px}.quiz-option.correct{border-color:var(--success);background:rgba(94,224,160,.14)}.quiz-option.wrong{border-color:var(--danger);background:rgba(255,138,138,.14)}.design-board{position:relative;min-height:320px;background:linear-gradient(var(--surface-2) 1px,transparent 1px) 0 0 /24px 24px,linear-gradient(90deg,var(--surface-2) 1px,transparent 1px) 0 0 /24px 24px,var(--surface);border:1px solid var(--border);border-radius:var(--radius);overflow:hidden}.design-node{position:absolute;min-width:96px;padding:8px 12px;background:var(--surface-2);border:2px solid 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.grad{background:linear-gradient(100deg,var(--accent-strong),var(--success));-webkit-background-clip:text;background-clip:text;color:transparent}.hero-sub{font-size:clamp(1.05rem,2.2vw,1.35rem);color:var(--text-muted);max-width:38ch;margin-bottom:28px}.cta-row{display:flex;flex-wrap:wrap;gap:14px;align-items:center}.btn-lg{font-size:1.05rem;padding:14px 26px}.hero-card{background:var(--surface);border:1px solid var(--border);border-radius:16px;box-shadow:var(--shadow);padding:14px;display:grid;grid-template-columns:1.3fr 1fr;grid-gap:12px;gap:12px;min-height:260px}.hero-card .page{background:#fff;border-radius:8px;padding:16px;color:#1a2233}.hero-card .page .ln{height:9px;border-radius:4px;background:#d7deea;margin-bottom:9px}.hero-card .page .ln.short{width:55%}.hero-card .panel{display:flex;flex-direction:column;gap:8px}.hero-card .pill{font-size:.8rem;font-weight:700;padding:6px 10px;border-radius:8px;background:var(--surface-2);border:1px solid var(--border);color:var(--text-muted)}.hero-card .pill.on{background:var(--accent);color:var(--accent-ink);border-color:var(--accent)}.section{max-width:1100px;margin:0 auto;padding:clamp(48px,7vw,88px) 24px}.section h2{font-size:clamp(1.7rem,3.4vw,2.4rem);letter-spacing:-.02em}.section .lead{color:var(--text-muted);font-size:1.1rem;max-width:60ch}.feature-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(260px,1fr));grid-gap:18px;gap:18px;margin-top:32px}.feature{background:var(--surface);border:1px solid var(--border);border-radius:14px;padding:22px}.feature .ic{font-size:1.7rem;line-height:1;margin-bottom:12px}.feature h3{margin-bottom:6px}.feature p{color:var(--text-muted);margin:0}.steps{list-style:none;padding:0;display:grid;grid-template-columns:repeat(auto-fit,minmax(240px,1fr));grid-gap:18px;gap:18px;margin-top:32px}.step{background:var(--surface);border:1px solid var(--border);border-radius:14px;padding:24px 22px}.step .num{display:inline-flex;align-items:center;justify-content:center;width:38px;height:38px;border-radius:10px;font-weight:800;font-size:1.1rem;background:var(--accent);color:var(--accent-ink);margin-bottom:14px}.step h3{margin-bottom:6px}.step p{color:var(--text-muted);margin:0}.lang-strip{display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));grid-gap:16px;gap:16px;margin-top:32px}.lang-card{background:var(--surface);border:1px solid var(--border);border-radius:14px;padding:20px}.lang-card .lang-badge{display:inline-flex;align-items:center;justify-content:center;min-width:52px;height:36px;padding:0 14px;border-radius:9px;font-weight:800;font-size:1rem;color:#ffffff;margin-bottom:12px;letter-spacing:.02em}.lang-card h3{margin-bottom:6px;font-size:1.1rem}.lang-card p{color:var(--text-muted);margin:0;font-size:.95rem}.lang-card .run{display:inline-block;margin-top:10px;font-size:.82rem;font-weight:700;color:var(--accent-strong)}.assure{display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));grid-gap:18px;gap:18px;margin-top:28px}.assure .item{display:flex;gap:12px;align-items:flex-start}.assure .item .ic{font-size:1.4rem}.cta-band{border-top:1px solid var(--border);background:color-mix(in srgb,var(--accent) 10%,var(--bg))}.cta-band .section,.landing-footer{text-align:center}.landing-footer{border-top:1px solid var(--border);color:var(--text-muted);padding:28px 24px;font-size:.95rem}@media (prefers-reduced-motion:reduce){*,:after,:before{animation-duration:.001ms!important;transition-duration:.001ms!important;scroll-behavior:auto!important}}