:root{--color-paper:oklch(13% .014 265);--color-paper-2:oklch(16% .014 265);--color-paper-3:oklch(19% .016 265);--color-paper-emit:oklch(76% .17 50/.04);--color-ink:oklch(96% .006 262);--color-ink-2:oklch(82% .008 262);--color-ink-3:oklch(62% .008 262);--color-muted:oklch(52% .006 262);--color-accent:oklch(76% .17 50);--color-accent-2:oklch(68% .16 18);--color-glow:oklch(80% .16 50/.42);--color-rule:oklch(96% .006 262/.07);--color-rule-2:oklch(96% .006 262/.12);--rule-blueprint:oklch(96% .006 262/.04);--color-l1:oklch(72% .15 280);--color-l2:oklch(72% .16 220);--color-l3:oklch(72% .14 160);--color-l4:oklch(72% .16 50);--color-l5:oklch(68% .16 18);--font-display:"Instrument Serif", "Tiempos Headline", ui-serif, Georgia, serif;--font-body:"Inter", system-ui, -apple-system, sans-serif;--font-mono:"JetBrains Mono", ui-monospace, monospace;--space-xs:4px;--space-sm:8px;--space-md:16px;--space-lg:24px;--space-xl:32px;--text-xs:.7rem;--text-sm:.8rem;--text-base:.9rem;--text-lg:1.05rem;--text-xl:1.25rem;--ease-out:cubic-bezier(.22, 1, .36, 1);--ease-soft:cubic-bezier(.25, .46, .45, .94);--dur-fast:.15s;--dur-base:.22s;--radius-sm:6px;--radius-md:10px;--radius-lg:14px}*,:before,:after{box-sizing:border-box;margin:0;padding:0}html,body{overflow-x:clip}html{scroll-behavior:smooth;font-size:14px}body{background:var(--color-paper);color:var(--color-ink-2);font-family:var(--font-body);font-variant-numeric:tabular-nums;-webkit-font-smoothing:antialiased;min-height:100dvh}::-webkit-scrollbar{width:5px;height:5px}::-webkit-scrollbar-track{background:0 0}::-webkit-scrollbar-thumb{background:var(--color-rule-2);border-radius:2px}.app-shell{background:var(--color-paper);min-height:100dvh;display:flex;position:relative}.sidebar{background:var(--color-paper-2);border-right:1px solid var(--color-rule);z-index:50;width:250px;height:100dvh;transition:transform var(--dur-base) var(--ease-out);flex-direction:column;flex-shrink:0;display:flex;position:sticky;top:0;overflow-y:auto}.sidebar-brand{padding:var(--space-md);border-bottom:1px solid var(--color-rule)}.brand-header-row{justify-content:space-between;align-items:center;display:flex}.brand-eyebrow{font-family:var(--font-mono);letter-spacing:.12em;text-transform:uppercase;color:var(--color-muted);font-size:9px}.mobile-close-btn{color:var(--color-ink-3);cursor:pointer;border-radius:var(--radius-sm);background:0 0;border:none;padding:4px;display:none}.mobile-close-btn:hover{color:var(--color-ink);background:var(--color-paper-3)}.mobile-close-btn:focus-visible,.mobile-menu-btn:focus-visible,.step-btn:focus-visible,.check-btn:focus-visible,.open-standalone-btn:focus-visible,.language-toggle:focus-visible{outline:2px solid var(--color-accent);outline-offset:2px}.brand-name{font-family:var(--font-display);color:var(--color-ink);letter-spacing:-.01em;margin-top:6px;font-size:1.15rem;line-height:1.3}.brand-name em{color:var(--color-accent);font-style:normal;position:relative}.brand-name em:after{content:"";background:var(--color-accent);height:1px;position:absolute;bottom:0;left:0;right:0}.countdown{padding:10px var(--space-md);border-bottom:1px solid var(--color-rule);font-family:var(--font-mono);background:oklch(76% .17 50/.05)}.countdown-label{color:var(--color-muted);text-transform:uppercase;letter-spacing:.08em;align-items:center;gap:6px;margin-bottom:4px;font-size:9px;display:flex}.countdown-time{color:var(--color-accent);letter-spacing:.02em;font-size:.8rem;font-weight:600}.study-progress-card{padding:10px var(--space-md);border-bottom:1px solid var(--color-rule);background:oklch(96% .006 262/.015)}.progress-header{font-family:var(--font-mono);justify-content:space-between;align-items:center;margin-bottom:6px;font-size:10px;display:flex}.progress-title{color:var(--color-ink-3);align-items:center;gap:5px;display:flex}.progress-value{color:var(--color-accent);font-weight:600}.progress-track{background:var(--color-paper-3);border-radius:2px;height:4px;overflow:hidden}.progress-fill{background:linear-gradient(90deg, var(--color-accent), var(--color-accent-2));height:100%;transition:width var(--dur-base) var(--ease-out)}.sidebar-nav{padding:var(--space-sm) 0;flex:1}.nav-section-label{font-family:var(--font-mono);letter-spacing:.12em;text-transform:uppercase;color:var(--color-muted);padding:0 var(--space-md);margin-top:14px;margin-bottom:6px;font-size:9px}.nav-section-label:first-child{margin-top:4px}.nav-item{padding:8px var(--space-md);font-size:var(--text-sm);color:var(--color-ink-3);cursor:pointer;transition:all var(--dur-fast) var(--ease-out);text-align:left;-webkit-user-select:none;user-select:none;background:0 0;border-left:2px solid #0000;align-items:center;gap:8px;width:100%;text-decoration:none;display:flex}.nav-item:hover{color:var(--color-ink);background:oklch(96% .006 262/.03)}.nav-item.active{color:var(--color-ink);border-left-color:var(--color-accent);background:oklch(76% .17 50/.08)}.nav-dot{border-radius:50%;flex-shrink:0;width:6px;height:6px}.nav-icon{opacity:.7;flex-shrink:0}.nav-item.active .nav-icon{opacity:1;color:var(--color-accent)}.nav-text-group{flex-direction:column;flex:1;min-width:0;display:flex}.nav-lecture-code{font-family:var(--font-mono);color:var(--color-muted);letter-spacing:.06em;font-size:9px}.nav-lecture-title{white-space:nowrap;text-overflow:ellipsis;font-size:11.5px;font-weight:500;overflow:hidden}.check-btn{color:var(--color-muted);cursor:pointer;transition:color var(--dur-fast);background:0 0;border:none;border-radius:4px;justify-content:center;align-items:center;padding:3px;display:flex}.check-btn:hover{color:var(--color-ink)}.check-btn.done{color:var(--color-l3)}.nav-item.external{color:var(--color-ink-3)}.nav-ext-icon{opacity:.4;margin-left:auto}.sidebar-footer{padding:12px var(--space-md);border-top:1px solid var(--color-rule);font-family:var(--font-mono);color:var(--color-muted);font-size:9.5px}.mobile-language-row{padding:10px var(--space-md);border-bottom:1px solid var(--color-rule);display:none}.language-toggle{border:1px solid var(--color-rule-2);border-radius:var(--radius-sm);background:var(--color-paper-2);min-height:30px;color:var(--color-muted);font-family:var(--font-mono);letter-spacing:.08em;white-space:nowrap;cursor:pointer;transition:background-color var(--dur-fast) var(--ease-out), border-color var(--dur-fast) var(--ease-out), color var(--dur-fast) var(--ease-out), transform .1s 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var(--color-rule);-webkit-backdrop-filter:blur(12px);backdrop-filter:blur(12px);z-index:40;padding:0 var(--space-md);align-items:center;gap:var(--space-md);background:oklch(13% .014 265/.96);flex-shrink:0;height:48px;display:flex;position:sticky;top:0}.mobile-menu-btn{border:1px solid var(--color-rule-2);color:var(--color-ink-2);cursor:pointer;border-radius:var(--radius-sm);background:0 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