:root{--primary: #2563EB;--primary-dark: #1D4ED8;--primary-light: #3B82F6;--secondary: #475569;--secondary-dark: #334155;--success: #10B981;--success-light: #34D399;--error: #EF4444;--error-light: #F87171;--warning: #F59E0B;--warning-light: #FBBF24;--info: #2563EB;--bg-main: #FFFFFF;--bg-alt: #F8FAFC;--bg-card: #FFFFFF;--bg-dark: #0F172A;--bg-overlay: rgba(0, 0, 0, .5);--text-primary: #0F172A;--text-secondary: #475569;--text-muted: #64748B;--text-inverse: #FFFFFF;--border: #E2E8F0;--border-light: #E2E8F0;--border-focus: var(--primary);--ring-color: #BFDBFE;--shadow-sm: none;--shadow-md: none;--shadow-lg: none;--shadow-xl: none;--radius-sm: 4px;--radius-md: 4px;--radius-lg: 4px;--radius-xl: 4px;--radius-full: 4px;--space-1: 4px;--space-2: 8px;--space-3: 12px;--space-4: 16px;--space-5: 20px;--space-6: 24px;--space-7: 32px;--space-8: 40px;--space-9: 48px;--space-10: 64px;--font-xs: .75rem;--font-sm: .875rem;--font-base: 1rem;--font-lg: 1.125rem;--font-xl: 1.25rem;--font-2xl: 1.5rem;--font-3xl: 2rem;--font-4xl: 2.5rem;--font-normal: 400;--font-medium: 500;--font-semibold: 600;--font-bold: 700;--font-sans: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;--font-mono: "JetBrains Mono", "Fira Code", "Consolas", monospace;--transition-fast: all .15s ease;--transition: all .15s ease;--transition-slow: all .2s ease;--touch-target-min: 36px;--z-dropdown: 100;--z-sticky: 200;--z-modal: 1000;--z-toast: 2000}@media(prefers-contrast:more){:root{--primary: #1d4ed8;--secondary: #334155;--text-primary: #000000;--text-secondary: #1e293b;--border: #94a3b8;--bg-alt: #f1f5f9}}*{margin:0;padding:0;box-sizing:border-box}.skip-link{position:absolute;top:-100%;left:0;background:#000;color:#fff;padding:8px 16px;z-index:10000;text-decoration:none;border-radius:0 0 4px;font-weight:600;opacity:0;pointer-events:none;transition:opacity .1s ease}.skip-link:focus{top:0;opacity:1;pointer-events:auto}:focus-visible{outline:3px solid var(--primary);outline-offset:2px}:focus:not(:focus-visible){outline:none}button:focus-visible,a:focus-visible,input:focus-visible,select:focus-visible,textarea:focus-visible{outline:3px solid var(--primary);outline-offset:2px}.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}@media(prefers-reduced-motion:reduce){*,*:before,*:after{animation-duration:.01ms!important;animation-iteration-count:1!important;transition-duration:.01ms!important}}body{font-family:var(--font-sans);line-height:1.5;color:var(--text-primary);background:var(--bg-main);min-height:100vh;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale}.container{max-width:1200px;margin:0 auto;padding:20px}header{text-align:center;padding:40px 20px;background:var(--bg-dark);color:#fff;border-radius:4px;margin-bottom:40px}header h1{font-size:2.5rem;margin-bottom:10px}header .tagline{font-size:1.1rem;opacity:.9}footer{text-align:center;padding:30px 20px;color:var(--text-secondary);font-size:.9rem}.btn{display:inline-flex;align-items:center;justify-content:center;padding:0 16px;height:36px;min-height:36px;border:1px solid transparent;border-radius:4px;font-family:var(--font-sans);font-size:14px;font-weight:500;cursor:pointer;transition:var(--transition-fast);text-decoration:none;text-align:center;line-height:1;white-space:nowrap}.btn-primary{background:var(--primary);color:#fff;border-color:var(--primary)}.btn-primary:hover:not(:disabled){background:var(--primary-dark);border-color:var(--primary-dark)}.btn-secondary{background:var(--bg-main);color:var(--text-primary);border-color:var(--border)}.btn-secondary:hover:not(:disabled){background:var(--bg-alt);border-color:var(--border)}.btn-large{height:44px;padding:0 24px;font-size:15px}.btn-small{height:28px;padding:0 12px;font-size:12px}.btn-full{width:100%}.btn:disabled{opacity:.5;cursor:not-allowed}.btn-ghost{background:transparent;color:var(--primary);border-color:var(--primary)}.btn-ghost:hover:not(:disabled){background:var(--primary);color:var(--text-inverse)}.btn-danger{background:var(--error);color:var(--text-inverse);border-color:var(--error)}.btn-danger:hover:not(:disabled){background:#dc2626;border-color:#dc2626}.btn-text{background:transparent;color:var(--primary);border-color:transparent;height:auto;padding:4px 8px}.btn-text:hover:not(:disabled){background:#2563eb14}.btn-success{background:var(--success);color:var(--text-inverse);border-color:var(--success)}.btn-success:hover:not(:disabled){background:#059669;border-color:#059669}.btn-icon{display:inline-flex;align-items:center;gap:var(--space-2)}.btn-loading{position:relative;color:transparent!important;pointer-events:none}.btn-loading:after{content:"";position:absolute;top:50%;left:50%;width:20px;height:20px;margin:-10px 0 0 -10px;border:2px solid currentColor;border-right-color:transparent;border-radius:50%;animation:spin .6s linear infinite}@keyframes spin{to{transform:rotate(360deg)}}.input-field,.answer-input{width:100%;height:36px;padding:0 12px;border:1px solid var(--border);border-radius:4px;font-size:14px;font-family:var(--font-sans);color:var(--text-primary);background:var(--bg-main);transition:var(--transition-fast)}.input-field:focus,.answer-input:focus{outline:none;border-color:var(--primary);box-shadow:0 0 0 2px var(--ring-color)}.input-group{margin-bottom:20px}.input-group label{display:block;margin-bottom:8px;font-weight:500;color:var(--text-primary)}.input-group small{display:block;margin-top:6px;color:var(--text-secondary);font-size:.875rem}.input-hint{display:block;margin-top:6px;color:var(--text-secondary);font-size:.85rem;font-style:italic}textarea.input-field{resize:vertical;min-height:100px}.input-field.error,.answer-input.error{border-color:var(--error);background:#fef2f2}.input-field.error:focus,.answer-input.error:focus{border-color:var(--error);box-shadow:0 0 0 3px #dc262626}.input-field.success,.answer-input.success{border-color:var(--success);background:#f0fdf4}.input-field.success:focus,.answer-input.success:focus{border-color:var(--success);box-shadow:0 0 0 3px #05966926}.input-error{display:block;margin-top:var(--space-2);color:var(--error);font-size:var(--font-sm)}.input-with-icon{position:relative}.input-with-icon .input-field{padding-left:44px}.input-with-icon .input-icon{position:absolute;left:14px;top:50%;transform:translateY(-50%);color:var(--text-muted);pointer-events:none}.checkbox-group,.radio-group{display:flex;flex-direction:column;gap:var(--space-3)}.checkbox-label,.radio-label{display:flex;align-items:center;gap:var(--space-3);cursor:pointer;padding:var(--space-2);border-radius:var(--radius-md);transition:var(--transition-fast)}.checkbox-label:hover,.radio-label:hover{background:var(--bg-alt)}.checkbox-label input,.radio-label input{width:20px;height:20px;accent-color:var(--primary)}.role-selector{display:grid;grid-template-columns:repeat(auto-fit,minmax(280px,1fr));gap:30px;margin:40px 0}.role-card{background:var(--bg-card);border:2px solid var(--border);border-radius:var(--radius-lg);padding:40px;text-align:center;transition:var(--transition);cursor:pointer}.role-card:hover{border-color:var(--primary);background:var(--bg-alt)}.role-card .icon{font-size:4rem;margin-bottom:20px}.role-card h2{margin-bottom:10px;color:var(--text-primary)}.role-card p{color:var(--text-secondary);margin-bottom:20px}.modal{position:fixed;top:0;left:0;width:100%;height:100%;background:var(--bg-overlay);backdrop-filter:blur(4px);-webkit-backdrop-filter:blur(4px);display:flex;align-items:center;justify-content:center;z-index:var(--z-modal);animation:modalFadeIn .2s ease}@keyframes modalFadeIn{0%{opacity:0}to{opacity:1}}.modal-content{background:var(--bg-card);padding:var(--space-8);border-radius:var(--radius-xl);max-width:500px;width:90%;max-height:90vh;overflow-y:auto;position:relative;box-shadow:var(--shadow-xl);animation:modalSlideIn .25s ease}@keyframes modalSlideIn{0%{opacity:0;transform:translateY(-20px) scale(.95)}to{opacity:1;transform:translateY(0) scale(1)}}.modal-content h2{margin-bottom:24px}.modal .close{position:absolute;top:16px;right:20px;font-size:28px;font-weight:700;color:var(--text-secondary);cursor:pointer;line-height:1}.modal .close:hover{color:var(--text-primary)}.link-text{text-align:center;margin-top:16px;color:var(--text-secondary)}.link-text a{color:var(--primary);text-decoration:none}.link-text a:hover{text-decoration:underline}.error-message,.status-message{padding:12px 16px;border-radius:var(--radius-md);margin-top:16px;font-size:.95rem}.error-message,.status-message.error{background:#fef2f2;border:1px solid #fecaca;color:#991b1b}.status-message.success{background:#f0fdf4;border:1px solid #bbf7d0;color:#166534}.status-message.info{background:#eff6ff;border:1px solid #bfdbfe;color:#1e40af}.status-message.warning{background:#fffbeb;border:1px solid #fde68a;color:#92400e}.toast-notification{position:fixed;bottom:24px;right:24px;background:var(--text-primary);color:var(--text-inverse);padding:var(--space-4) var(--space-6);border-radius:var(--radius-md);box-shadow:var(--shadow-lg);z-index:var(--z-toast);opacity:1;animation:toastSlideIn .3s ease;display:flex;align-items:center;gap:var(--space-3);max-width:400px}@keyframes toastSlideIn{0%{opacity:0;transform:translateY(20px)}to{opacity:1;transform:translateY(0)}}.toast-notification.success{background:var(--success)}.toast-notification.error{background:var(--error)}.toast-notification.warning{background:var(--warning)}.focus-trap-active{overflow:hidden}.focusable:focus-visible,[tabindex]:focus-visible{outline:3px solid var(--primary);outline-offset:2px}.skip-link:focus{top:0;left:0;padding:var(--space-3) var(--space-5);font-size:var(--font-base)}.selectable-card{cursor:pointer;transition:var(--transition)}.selectable-card:focus-visible{outline:3px solid var(--primary);outline-offset:2px;box-shadow:var(--shadow-md)}.selectable-card:focus-visible,.selectable-card:hover{border-color:var(--primary);transform:translateY(-2px)}.nav-list-item{padding:var(--space-3) var(--space-4);border-radius:var(--radius-md);cursor:pointer;transition:var(--transition-fast)}.nav-list-item:hover,.nav-list-item:focus-visible{background:var(--bg-alt)}.nav-list-item:focus-visible{outline:2px solid var(--primary);outline-offset:-2px}.nav-list-item.active{background:#2563eb1a;color:var(--primary);font-weight:var(--font-medium)}.answer-option{display:flex;align-items:center;padding:var(--space-4);border:2px solid var(--border);border-radius:var(--radius-md);cursor:pointer;transition:var(--transition-fast);gap:var(--space-3)}.answer-option:hover{border-color:var(--primary-light);background:#2563eb0d}.answer-option:focus-visible{outline:none;border-color:var(--primary);box-shadow:0 0 0 3px #2563eb33}.answer-option.selected{border-color:var(--primary);background:#2563eb1a}.answer-option.correct{border-color:var(--success);background:#0596691a}.answer-option.incorrect{border-color:var(--error);background:#dc26261a}.kbd{display:inline-block;padding:2px 6px;font-family:ui-monospace,SFMono-Regular,Menlo,Monaco,Consolas,monospace;font-size:var(--font-xs);color:var(--text-secondary);background:var(--bg-alt);border:1px solid var(--border);border-radius:var(--radius-sm)}.placeholder{text-align:center;color:var(--text-secondary);padding:40px}.empty-state{text-align:center;color:var(--text-secondary);padding:var(--space-10) var(--space-5);font-size:var(--font-lg)}.empty-state-icon{font-size:4rem;margin-bottom:var(--space-5);opacity:.5}.empty-state-title{font-size:var(--font-xl);font-weight:var(--font-semibold);color:var(--text-primary);margin-bottom:var(--space-3)}.empty-state-description{color:var(--text-secondary);margin-bottom:var(--space-6);max-width:400px;margin-left:auto;margin-right:auto}.skeleton{background:linear-gradient(90deg,var(--bg-alt) 0%,#e2e8f0 50%,var(--bg-alt) 100%);background-size:200% 100%;animation:shimmer 1.5s infinite;border-radius:var(--radius-md)}@keyframes shimmer{0%{background-position:200% 0}to{background-position:-200% 0}}.skeleton-text{height:1rem;margin-bottom:var(--space-2)}.skeleton-text:last-child{width:70%}.skeleton-title{height:1.5rem;width:60%;margin-bottom:var(--space-4)}.skeleton-button{height:44px;width:120px}.skeleton-card{padding:var(--space-6);border:1px solid var(--border-light);border-radius:var(--radius-lg)}.skeleton-lesson-item{display:flex;align-items:center;gap:var(--space-4);padding:var(--space-4);border:1px solid var(--border-light);border-radius:var(--radius-md);margin-bottom:var(--space-3)}.skeleton-lesson-icon{width:48px;height:48px;border-radius:var(--radius-md);flex-shrink:0}.skeleton-lesson-content{flex:1}.spinner{display:inline-block;width:24px;height:24px;border:3px solid var(--border);border-top-color:var(--primary);border-radius:50%;animation:spin .8s linear infinite}.spinner-lg{width:40px;height:40px;border-width:4px}.spinner-sm{width:16px;height:16px;border-width:2px}.loading-overlay{position:absolute;inset:0;background:#fffc;display:flex;align-items:center;justify-content:center;z-index:var(--z-dropdown)}.offline-indicator{position:fixed;bottom:var(--space-4);left:50%;transform:translate(-50%);background:var(--text-primary);color:var(--text-inverse);padding:var(--space-3) var(--space-5);border-radius:4px;font-size:var(--font-sm);font-weight:var(--font-medium);display:flex;align-items:center;gap:var(--space-2);z-index:var(--z-toast);animation:slideUp .3s ease}.offline-indicator:before{content:"";width:8px;height:8px;background:var(--warning);border-radius:50%;animation:pulse 2s infinite}@keyframes slideUp{0%{opacity:0;transform:translate(-50%) translateY(20px)}to{opacity:1;transform:translate(-50%) translateY(0)}}@keyframes pulse{0%,to{opacity:1}50%{opacity:.5}}.progress-bar{height:8px;background:#e2e8f0;border-radius:4px;overflow:hidden;position:relative}.progress-bar-fill{height:100%;background:var(--primary);border-radius:4px;transition:width .5s ease;position:relative}.progress-bar-lg{height:12px}.progress-bar-sm{height:4px}.progress-label{display:flex;justify-content:space-between;align-items:center;margin-bottom:var(--space-2);font-size:var(--font-sm);color:var(--text-secondary)}.progress-label-value{font-weight:var(--font-semibold);color:var(--text-primary)}.hidden{display:none!important}.text-center{text-align:center}.mb-1{margin-bottom:8px}.mb-2{margin-bottom:16px}.mb-3{margin-bottom:24px}.mb-4{margin-bottom:32px}.mt-1{margin-top:8px}.mt-2{margin-top:16px}.mt-3{margin-top:24px}.mt-4{margin-top:32px}@media(max-width:768px){header h1{font-size:2rem}.role-selector{grid-template-columns:1fr}.modal-content{padding:24px}.btn-large{padding:14px 24px;font-size:1rem}}@keyframes fadeIn{0%{opacity:0;transform:translateY(10px)}to{opacity:1;transform:translateY(0)}}.screen{display:none;animation:fadeIn .3s ease}.screen.active{display:block}:focus-visible{outline:2px solid var(--primary);outline-offset:2px}.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border-width:0}@media(prefers-contrast:high){:root{--border: #000000}.btn{border:2px solid currentColor}}@media(prefers-reduced-motion:reduce){*{animation-duration:.01ms!important;animation-iteration-count:1!important;transition-duration:.01ms!important}}.logout-link{margin-top:20px;text-align:center}.logout-link a{color:var(--text-secondary);font-size:.85rem;text-decoration:none}.logout-link a:hover{color:var(--text-primary);text-decoration:underline}.topic-header{display:flex;justify-content:space-between;align-items:center;margin-bottom:20px;flex-wrap:wrap;gap:10px}.topic-header h2{margin:0}.form-row-2col{display:grid;grid-template-columns:1fr 1fr;gap:20px;margin-bottom:20px}@media(max-width:600px){.form-row-2col{grid-template-columns:1fr}}.student-badge{display:flex;align-items:center;gap:10px;background:#ffffff1a;padding:8px 12px;border-radius:4px;font-size:.9rem}.switch-link{color:var(--accent);text-decoration:none;font-size:.8rem}.switch-link:hover{text-decoration:underline}.table-wrapper{overflow-x:auto;margin:16px 0;border-radius:var(--radius-md);box-shadow:var(--shadow-sm)}.markdown-table{width:100%;border-collapse:collapse;background:var(--bg-card);font-size:.95rem;min-width:300px}.markdown-table th,.markdown-table td{padding:12px 16px;text-align:left;border:1px solid var(--border);vertical-align:top}.markdown-table th{background:var(--bg-dark);color:#fff;font-weight:600}.markdown-table tbody tr:nth-child(2n){background:var(--bg-alt)}.markdown-table tbody tr:hover{background:#2563eb0d}.markdown-table td strong{color:var(--primary)}.markdown-table td:first-child{font-weight:500}@media(max-width:600px){.markdown-table{font-size:.85rem}.markdown-table th,.markdown-table td{padding:8px 10px}}.review-moment{text-align:center;padding:var(--space-8) var(--space-6);max-width:600px;margin:0 auto}.review-moment .review-icon{font-size:3rem;margin-bottom:var(--space-4)}.review-moment h3{color:var(--text-primary);font-size:var(--font-xl);font-weight:var(--font-semibold);margin-bottom:var(--space-4)}.review-moment p{color:var(--text-secondary);font-size:var(--font-base);line-height:1.6;margin-bottom:var(--space-4)}.review-moment .review-encouragement{color:var(--primary);font-weight:var(--font-medium);font-style:italic}.review-moment .review-tips{text-align:left;background:var(--bg-alt);border:1px solid var(--border);border-radius:var(--radius-md);padding:var(--space-4);margin:var(--space-6) 0}.review-moment .review-tips h4{color:var(--text-primary);font-size:var(--font-sm);font-weight:var(--font-semibold);margin-bottom:var(--space-3)}.review-moment .review-tips ul{margin:0;padding-left:var(--space-5)}.review-moment .review-tips li{color:var(--text-secondary);font-size:var(--font-sm);margin-bottom:var(--space-2)}.review-moment .review-tips li:last-child{margin-bottom:0}.review-moment #continue-to-assessment{margin-top:var(--space-4);min-width:200px}.beta-badge{display:inline-block;background:linear-gradient(135deg,#f59e0b,#d97706);color:#fff;font-size:10px;font-weight:600;letter-spacing:.05em;text-transform:uppercase;padding:2px 6px;border-radius:4px;margin-left:8px;vertical-align:middle;box-shadow:0 1px 2px #0000001a}.storage-info{display:flex;flex-direction:column;gap:var(--space-1);flex:1}.storage-bar{width:100%;height:8px;background:var(--bg-alt);border:1px solid var(--border);border-radius:var(--radius-sm);overflow:hidden}.storage-fill{height:100%;background:var(--primary);transition:width .3s ease,background-color .3s ease}.storage-fill.storage-high{background:var(--warning)}.storage-fill.storage-critical{background:var(--error)}.storage-text{font-size:var(--font-sm);color:var(--text-secondary)}.storage-info.storage-high .storage-text{color:var(--warning);font-weight:var(--font-medium)}.storage-info.storage-critical .storage-text{color:var(--error);font-weight:var(--font-semibold)}.storage-warning{display:flex;align-items:center;gap:var(--space-2);padding:var(--space-3) var(--space-4);border-radius:var(--radius-md);margin-bottom:var(--space-4);font-size:var(--font-sm)}.storage-warning.storage-high{background:#f59e0b1a;border:1px solid var(--warning);color:#92400e}.storage-warning.storage-critical{background:#ef44441a;border:1px solid var(--error);color:#991b1b}.storage-warning .warning-icon{font-size:var(--font-lg)}.storage-warning .warning-text{flex:1}.class-switcher{position:relative;display:inline-block;margin-right:var(--space-3)}.class-switcher-btn{display:flex;align-items:center;gap:var(--space-2);padding:var(--space-2) var(--space-3);background:var(--bg-alt);border:1px solid var(--border);border-radius:var(--radius-md);cursor:pointer;font-size:var(--font-sm);color:var(--text-primary);transition:all .15s ease}.class-switcher-btn:hover{background:var(--bg-main);border-color:var(--primary)}.class-switcher-btn:focus{outline:none;box-shadow:0 0 0 2px var(--ring-color)}.class-switcher-btn .class-icon{font-size:var(--font-base)}.class-switcher-btn .count-badge{display:inline-flex;align-items:center;justify-content:center;min-width:20px;height:20px;padding:0 6px;background:var(--primary);color:#fff;font-size:11px;font-weight:var(--font-semibold);border-radius:10px}.class-switcher-btn .dropdown-arrow{font-size:10px;color:var(--text-muted);transition:transform .2s ease}.class-dropdown{position:absolute;top:calc(100% 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