:root{--bg:#f5f7fa;--panel:#ffffff;--panel-header:#f8f9fb;--surface:#ffffff;--surface-muted:#f9fafb;--surface-hover:#f9fafb;--text-strong:#374151;--border-hover:#9ca3af;--menu-bar-bg:#3c3c3c;--menu-text-color:#ffffff;--menu-dropdown-border:#d0d0d0;--menu-link-text:#1d1d1f;--menu-link-hover-text:#ffffff;--menu-link-hover-bg:rgba(0, 122, 255, 0.95);--menu-link-active-bg:rgba(0, 106, 220, 0.95);--menu-link-focus-bg:#f3f4f6;--menu-link-disabled:#9ca3af;--menu-link-icon:#6e6e73;--border:#d1d5db;--border-soft:#e5e7eb;--text:#1f2937;--muted:#6b7280;--text-muted:#6b7280;--danger:#ef4444;--link:#3b82f6;--link-hover:#2563eb;--file-active-bg:#eff6ff;--file-active-text:#1e40af;--font-base:-apple-system, BlinkMacSystemFont, "SF Pro Text", "SF Pro Display", "Segoe UI", "Roboto", sans-serif;--font-mono:'SF Mono', Monaco, 'Cascadia Code', Consolas, monospace;--text-xs:0.75rem;--text-sm:0.875rem;--text-base:0.9375rem;--text-lg:1.125rem;--text-xl:1.25rem;--text-2xl:1.5rem;--weight-normal:400;--weight-medium:500;--weight-semibold:600;--weight-bold:700;--leading-tight:1.25;--leading-snug:1.375;--leading-normal:1.5;--leading-relaxed:1.625;--tracking-tight:-0.01em;--tracking-normal:0;--tracking-wide:0.025em;--space-0:0;--space-px:1px;--space-0-5:2px;--space-0-75:3px;--space-1:4px;--space-1-25:5px;--space-1-5:6px;--space-2:8px;--space-2-5:10px;--space-3:12px;--space-3-5:14px;--space-4:16px;--space-5:20px;--space-6:24px;--space-7:28px;--space-8:32px;--space-10:40px;--space-11:44px;--space-12:48px;--border-width-0:0;--border-width-1:1px;--border-width-2:2px;--border-width-4:4px;--radius-none:0;--radius-sm:2px;--radius-md:3px;--radius-base:8px;--radius-lg:12px;--radius-xl:16px;--radius-2xl:24px;--radius-full:9999px;--header-height:30px;--toggle-size:var(--space-6);--toggle-top:3px;--toggle-offset:var(--space-1);--radius:var(--radius-lg);--gap:0.75rem;--pad:1rem;--header-pad-y:0.875rem;--header-pad-x:1.25rem;--btn-bg:#f3f4f6;--btn-bg-hover:#e5e7eb;--btn-border:#d1d5db;--field-border:#d1d5db;--document-accent:#ef4444;--document-accent-soft:rgba(239, 68, 68, 0.12);--document-accent-bg:#fee2e2;--visual-accent:#8b5cf6;--visual-accent-soft:rgba(139, 92, 246, 0.12);--visual-accent-bg:#ede9fe;--audio-accent:#10b981;--audio-accent-strong:#059669;--audio-accent-deep:#047857;--audio-accent-bg:#d1fae5;--audio-accent-bg-strong:#a7f3d0;--audio-accent-border:#a7f3d0;--audio-accent-bg-soft:#ecfdf5;--audio-accent-bg-xsoft:#f0fdf4;--audio-accent-soft:rgba(16, 185, 129, 0.1);--audio-accent-text:#065f46;--shadow-sm:0 1px 2px 0 rgba(0, 0, 0, 0.05);--shadow-md:0 4px 6px -1px rgba(0, 0, 0, 0.1);--shadow-lg:0 10px 15px -3px rgba(0, 0, 0, 0.1);--duration-fast:120ms;--duration-base:400ms;--duration-slow:600ms;--duration-slower:800ms;--ease-out:cubic-bezier(0.16, 1, 0.3, 1);--ease-in-out:cubic-bezier(0.4, 0, 0.2, 1);--ease-spring:cubic-bezier(0.175, 0.885, 0.32, 1.275);--audio-time-width:84px;--ab-time-column:48px;--ab-actions-column:90px;--z-pane-layer:1;--z-iframe-loading:9;--z-pane-header:10;--z-right-pane-toggle:20;--z-menu-bar:1000;--z-menu-dropdown:1001;--z-menu-submenu:1002;--z-dialog:5000}*{box-sizing:border-box}html,body{height:100%;width:100%;margin:0;padding:0;overflow:auto;background:var(--bg);color:var(--text);font-family:var(--font-base);font-size:var(--text-base);font-weight:var(--weight-normal)}html.has-lesson,html.has-lesson body{overflow:hidden}body{display:flex;flex-direction:column;line-height:var(--leading-normal);letter-spacing:var(--tracking-tight);-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;text-rendering:optimizeLegibility}a{color:var(--link);transition:color var(--duration-fast)var(--ease-out)}a:hover{color:var(--link-hover)}a:focus-visible{outline:2px solid var(--link);outline-offset:2px;border-radius:2px;transition:outline-offset var(--duration-fast)var(--ease-out)}a:visited{color:var(--link)}.hidden{display:none!important}.muted{color:var(--muted);font-size:var(--text-base);font-weight:var(--weight-medium);letter-spacing:var(--tracking-tight);margin:0}h1,h2,h3,h4,h5,h6{font-family:var(--font-base);font-weight:var(--weight-bold);line-height:var(--leading-tight);letter-spacing:var(--tracking-tight);color:var(--text);margin-top:0}h1{font-size:var(--text-2xl);margin-bottom:1rem}h2{font-size:var(--text-xl);font-weight:var(--weight-semibold);margin-bottom:.75rem}h3{font-size:var(--text-lg);font-weight:var(--weight-semibold);line-height:var(--leading-snug);margin-bottom:.5rem}h4,h5,h6{font-size:var(--text-base);font-weight:var(--weight-semibold);margin-bottom:.5rem}.lesson-content p,.prose p{margin-bottom:1.25em;line-height:var(--leading-relaxed)}.lesson-content h2,.prose h2{margin-top:2em;margin-bottom:.75em}.lesson-content h3,.prose 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0}.lessons-list__empty{opacity:.75}.lessons-list__back{margin-top:1.5rem}.lesson-container{display:flex;flex:1;width:100%;max-width:100%;overflow:hidden;opacity:1;visibility:visible;transition:opacity .2s ease-in-out,visibility 0s 0s;contain:layout style paint}.lesson-container.lesson-loading{opacity:0;visibility:hidden;transition:opacity 0s,visibility 0s}.document-pane{border-radius:8px;border:1px solid var(--border);min-height:0;background:var(--surface);display:flex;flex-direction:column;contain:layout style}.pane-content{display:flex;flex-direction:column;flex:auto;min-height:0;padding:.5rem var(--pad);position:relative;z-index:var(--z-pane-layer);outline:none;transition:box-shadow var(--duration-base)var(--ease-out)}.pane-content:focus-visible{box-shadow:inset 0 0 0 2px var(--link)}@keyframes keyFeedback{0%{box-shadow:inset 0 0 0 2px var(--link)}50%{box-shadow:inset 0 0 0 3px var(--link),0 0 20px rgba(59,130,246,.4)}100%{box-shadow:inset 0 0 0 2px 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var(--audio-accent-border)}.toast-notification{position:fixed;bottom:24px;left:50%;transform:translateX(-50%)translateY(100%);background:rgba(0,0,0,.85);color:#fff;padding:12px 20px;border-radius:8px;font-size:14px;z-index:9999;opacity:0;transition:transform .3s ease,opacity .3s ease;pointer-events:none}.toast-notification.visible{transform:translateX(-50%)translateY(0);opacity:1}.cursor-tooltip{position:fixed;background:var(--text);color:var(--panel);padding:4px 10px;border-radius:4px;font-size:var(--text-xs);font-weight:var(--weight-medium);pointer-events:none;z-index:var(--z-dialog);white-space:nowrap;animation:cursorTooltipFade 1.5s ease-out forwards}@keyframes cursorTooltipFade{0%{opacity:1;transform:translateY(0)}70%{opacity:1;transform:translateY(0)}100%{opacity:0;transform:translateY(-8px)}}.document-abc-viewer{display:flex;flex-direction:column;flex:auto;gap:8px;width:100%;height:100%;min-height:0;overflow-y:auto;overflow-x:hidden;padding:6px 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slideDown{from{opacity:0;transform:translateY(-10px)}to{opacity:1;transform:translateY(0)}}.dialog-overlay{position:fixed;top:0;left:0;right:0;bottom:0;background:0 0;display:flex;align-items:center;justify-content:center;z-index:var(--z-dialog);transition:background-color .2s ease-out}.dialog-overlay.active{background:rgba(0,0,0,.4)}.dialog-window{background:#fff;border-radius:12px;box-shadow:0 20px 60px rgba(0,0,0,.3);width:90%;max-width:500px;max-height:80vh;display:flex;flex-direction:column;opacity:0;transform:scale(.9)translateY(-20px);transition:opacity .2s ease-out,transform .2s ease-out}.dialog-overlay.active .dialog-window{opacity:1;transform:scale(1)translateY(0)}.dialog-header{display:flex;align-items:center;justify-content:space-between;padding:20px 24px;border-bottom:1px solid var(--border-soft)}.dialog-header h2{margin:0;font-size:var(--text-lg);font-weight:var(--weight-semibold);color:var(--text)}.dialog-close{width:32px;height:32px;border:none;background:0 0;border-radius:6px;cursor:pointer;display:flex;align-items:center;justify-content:center;color:var(--muted);transition:background-color .2s ease,color .2s ease}.dialog-close:hover{background:var(--bg);color:var(--text)}.dialog-close i{font-size:18px}.dialog-body{padding:24px;overflow-y:auto;flex:1}.dialog-body p{margin:0 0 1em;line-height:var(--leading-relaxed);color:var(--text)}.dialog-body p:last-child{margin-bottom:0}.dialog-body ul{margin:.5em 0;padding-left:1.5em}.dialog-body li{margin:.5em 0;line-height:var(--leading-relaxed);color:var(--text)}.dialog-footer{padding:16px 24px;border-top:1px solid var(--border-soft);display:flex;justify-content:flex-end;gap:12px}.dialog-button{padding:8px 16px;border-radius:6px;font-size:var(--text-sm);font-weight:var(--weight-medium);border:1px solid var(--border);background:var(--btn-bg);color:var(--text);cursor:pointer;transition:background-color .2s ease,border-color .2s ease,box-shadow .2s ease,transform .2s ease,color .2s ease;font-family:inherit}.dialog-button:hover{background:var(--btn-bg-hover);border-color:var(--border-hover);transform:translateY(-1px);box-shadow:var(--shadow-sm)}.dialog-button.primary{background:var(--link);color:#fff;border-color:var(--link)}.dialog-button.primary:hover{background:var(--link-hover);border-color:var(--link-hover)}.keyboard-help-overlay{position:fixed;top:0;left:0;right:0;bottom:0;background:rgba(0,0,0,.75);z-index:10000;display:flex;align-items:center;justify-content:center;padding:20px;animation:fadeIn var(--duration-base)var(--ease-out)}.keyboard-help-overlay.hidden{display:none}.keyboard-help-content{background:var(--bg);border-radius:12px;padding:32px;max-width:800px;max-height:90vh;overflow-y:auto;box-shadow:0 20px 60px rgba(0,0,0,.3);position:relative;animation:scaleIn var(--duration-base)var(--ease-out)}.keyboard-help-close{position:absolute;top:16px;right:16px;background:0 0;border:none;font-size:2rem;color:var(--text-muted);cursor:pointer;width:40px;height:40px;display:flex;align-items:center;justify-content:center;border-radius:50%;transition:all var(--duration-fast)var(--ease-out)}.keyboard-help-close:hover{background:var(--surface-hover);color:var(--text)}.keyboard-help-content h2{margin:0 0 24px;font-size:var(--text-2xl);color:var(--text-strong);font-weight:var(--weight-bold)}.keyboard-help-section{margin-bottom:28px}.keyboard-help-section h3{font-size:var(--text-lg);color:var(--link);margin:0 0 12px;font-weight:var(--weight-semibold);border-bottom:2px solid var(--border-soft);padding-bottom:6px}.keyboard-help-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(200px,1fr));gap:12px}.keyboard-help-item{display:flex;align-items:center;gap:12px;padding:8px;background:var(--surface);border-radius:6px;transition:background var(--duration-fast)var(--ease-out)}.keyboard-help-item:hover{background:var(--surface-hover)}.keyboard-help-item kbd{background:linear-gradient(180deg,var(--bg) 0%,var(--surface) 100%);border:1px solid var(--border);border-bottom-width:2px;border-radius:4px;padding:4px 8px;font-family:var(--font-mono);font-size:.75rem;font-weight:var(--weight-semibold);color:var(--text-strong);box-shadow:0 2px 0 0 var(--border-soft);white-space:nowrap;min-width:28px;text-align:center}.keyboard-help-item span{font-size:.875rem;color:var(--text);flex:1}.keyboard-help-footer{margin-top:32px;padding-top:20px;border-top:2px solid var(--border-soft);text-align:center}.keyboard-help-footer p{margin:0;font-size:.875rem;color:var(--text-muted)}.keyboard-help-footer kbd{background:linear-gradient(180deg,var(--bg) 0%,var(--surface) 100%);border:1px solid var(--border);border-bottom-width:2px;border-radius:4px;padding:3px 8px;font-family:var(--font-mono);font-size:.75rem;font-weight:var(--weight-semibold);color:var(--link);box-shadow:0 2px 0 0 var(--border-soft)}@media(max-width:768px){.keyboard-help-content{padding:24px 20px;max-height:95vh}.keyboard-help-grid{grid-template-columns:1fr}}@media(min-width:1200px){:root{--text-base:1rem;--text-xl:1.375rem;--text-2xl:1.75rem}}@media(max-width:900px){:root{--text-base:0.875rem;--text-xl:1.125rem;--text-2xl:1.375rem}.lesson-container{flex-direction:column}}@media(prefers-reduced-motion:reduce){*,*::before,*::after{animation-duration:.01ms!important;animation-iteration-count:1!important;transition-duration:.01ms!important}}@supports(backdrop-filter:blur(4px)) or (-webkit-backdrop-filter:blur(4px)){.keyboard-help-overlay{backdrop-filter:blur(4px);-webkit-backdrop-filter:blur(4px)}}@supports not ((backdrop-filter:blur(4px)) or (-webkit-backdrop-filter:blur(4px))){.keyboard-help-overlay{background:rgba(0,0,0,.88)}}