:root{--space-xs:0.25rem;--space-sm:0.5rem;--space-md:1rem;--space-lg:1.5rem;--space-xl:2rem;--font-size-xs:0.75rem;--font-size-sm:0.875rem;--font-size-base:1rem;--font-size-lg:1.125rem;--font-size-xl:1.25rem;--font-size-2xl:1.5rem;--radius-sm:0.25rem;--radius-md:0.375rem;--radius-lg:0.5rem;--radius-full:50rem;--transition-normal:0.25s ease;--transition-slow:0.35s ease}*{margin:0;padding:0}body,html{font-family:system-ui,-apple-system,Segoe UI,Roboto,sans-serif;line-height:1.6;background-color:var(--bg-body)}.container{max-width:1280px;margin:0 auto;padding:0 1rem}@media(min-width:768px){.container{padding:0 1.5rem}}.visually-hidden{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}@keyframes bounce{0%,80%,to{transform:scale(0)}40%{transform:scale(1)}}@keyframes fadeIn{0%{opacity:0;transform:translateY(10px)}to{opacity:1;transform:translateY(0)}}@keyframes 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New,monospace;font-size:.875em}::-webkit-scrollbar{width:8px}::-webkit-scrollbar-track{background:var(--bg-elevated)}::-webkit-scrollbar-thumb{background:var(--text-muted);border-radius:var(--radius-md)}::-webkit-scrollbar-thumb:hover{background:var(--text-secondary)}:root{--primary-50:#eff6ff;--primary-100:#dbeafe;--primary-200:#bfdbfe;--primary-300:#93c5fd;--primary-400:#60a5fa;--primary-500:#3b82f6;--primary-600:#2563eb;--primary-700:#1d4ed8;--primary-800:#1e40af;--primary-900:#1e3a8a;--success-50:#f0fdf4;--success-100:#dcfce7;--success-200:#bbf7d0;--success-300:#86efac;--success-400:#4ade80;--success-500:#22c55e;--success-600:#16a34a;--success-700:#15803d;--success-800:#166534;--warning-50:#fffbeb;--warning-100:#fef3c7;--warning-200:#fde68a;--warning-300:#fcd34d;--warning-400:#fbbf24;--warning-500:#f59e0b;--warning-600:#d97706;--error-50:#fef2f2;--error-100:#fee2e2;--error-200:#fecaca;--error-300:#fca5a5;--error-400:#f87171;--error-500:#ef4444;--error-600:#dc2626;--gray-50:#f9fafb;--gray-100:#f3f4f6;--gray-200:#e5e7eb;--gray-300:#d1d5db;--gray-400:#9ca3af;--gray-500:#6b7280;--gray-600:#4b5563;--gray-700:#374151;--gray-800:#1f2937;--gray-900:#111827;--space-1:0.25rem;--space-2:0.5rem;--space-3:0.75rem;--space-4:1rem;--space-5:1.25rem;--space-6:1.5rem;--space-8:2rem;--space-10:2.5rem;--space-12:3rem;--space-16:4rem;--space-20:5rem;--font-primary:"Inter",-apple-system,BlinkMacSystemFont,"Segoe 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var(--space-8);line-height:1.6;font-weight:400}.feature-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(320px,1fr));grid-gap:var(--space-8);gap:var(--space-8);margin-top:var(--space-16)}.feature-card{background:rgba(255,255,255,.9);-webkit-backdrop-filter:blur(10px);backdrop-filter:blur(10px);border:1px solid rgba(255,255,255,.2);border-radius:16px;padding:var(--space-8);box-shadow:0 4px 6px -1px rgba(0,0,0,.1),0 2px 4px -1px rgba(0,0,0,.06);transition:all var(--transition-normal);position:relative;overflow:hidden}.feature-card:before{content:"";position:absolute;top:0;left:0;right:0;height:4px;background:linear-gradient(90deg,var(--primary-500),var(--primary-600));transform:translateX(-100%);transition:transform var(--transition-normal)}.feature-card:hover{transform:translateY(-8px);box-shadow:0 20px 25px -5px rgba(0,0,0,.1),0 10px 10px -5px 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0;text-align:center}.chat-title{font-size:28px;font-weight:600;color:#1e293b;margin-bottom:8px}.chat-subtitle{color:#64748b;font-size:16px}.topic-selector{display:flex;gap:8px;justify-content:center;flex-wrap:wrap;margin-top:20px}.topic-btn{padding:8px 16px;border-radius:20px;border:1px solid #e2e8f0;background:#ffffff;color:#64748b;text-decoration:none;font-size:14px;font-weight:500;transition:all .2s ease}.topic-btn:hover{background:#f1f5f9;border-color:#cbd5e1;color:#1e293b}.topic-btn.active{background:#3b82f6;color:white;border-color:#3b82f6}.difficulty-selector{display:grid;grid-template-columns:repeat(4,1fr);grid-gap:16px;gap:16px;max-width:800px;margin:32px auto 0}.difficulty-btn{padding:20px 16px;border-radius:12px;border:2px solid #e2e8f0;background:#ffffff;text-align:center;cursor:pointer;transition:all .2s ease}.difficulty-btn:hover{border-color:#3b82f6;transform:translateY(-2px);box-shadow:0 4px 12px rgba(0,0,0,.1)}.difficulty-btn.selected{border-color:#3b82f6;background:#dbeafe}.difficulty-title{font-weight:600;color:#1e293b;margin-bottom:6px;font-size:14px}.difficulty-desc{font-size:12px;color:#64748b;line-height:1.4}.quick-actions{padding:40px 0;text-align:center}.quick-actions h2{font-size:24px;font-weight:600;color:#1e293b;margin-bottom:32px}.action-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(280px,1fr));grid-gap:24px;gap:24px;max-width:900px;margin:0 auto}.action-card{padding:24px;border-radius:16px;border:1px solid #e2e8f0;background:#ffffff;text-decoration:none;transition:all .3s ease;text-align:left}.action-card:hover{border-color:#3b82f6;transform:translateY(-4px);box-shadow:0 8px 25px rgba(0,0,0,.08)}.action-icon{font-size:32px;margin-bottom:16px}.action-title{font-size:18px;font-weight:600;color:#1e293b;margin-bottom:8px}.action-desc{color:#64748b;line-height:1.5;font-size:14px}@media (max-width:768px){.dashboard-sidebar{width:60px}.dashboard-sidebar.collapsed{width:0}.chat-interface{padding:0 16px}.difficulty-selector{grid-template-columns:repeat(2,1fr);gap:12px}.chat-title{font-size:24px}.quick-actions h2{font-size:20px;margin-bottom:24px}}:root,html[data-theme=dark]{--color-brand-primary:#3b82f6;--color-brand-primary-alt:#2563eb;--color-brand-secondary:#8b5cf6;--color-brand-accent:#10b981;--color-brand-danger:#ef4444;--color-brand-warn:#f59e0b;--color-brand-success:#22c55e;--gray-50:#f5f7fa;--gray-100:#e6ebf1;--gray-200:#cfd6df;--gray-300:#a5adba;--gray-400:#7e8895;--gray-500:#5d6672;--gray-600:#454e59;--gray-700:#303841;--gray-800:#1c232a;--gray-850:#171d23;--gray-900:#11161b;--gray-950:#0c1014;--bg-body:var(--gray-950);--bg-surface:#111318;--bg-elevated:#171a21;--bg-overlay:rgba(15,17,21,0.72);--bg-accent-faint:linear-gradient(135deg,rgba(59,130,246,0.08),rgba(139,92,246,0.08));--border:#1f242c;--border-soft:#242a33;--border-strong:#2d353f;--focus-ring:#6366f1;--text-primary:var(--gray-50);--text-secondary:var(--gray-300);--text-muted:var(--gray-500);--text-inverse:#0f1115;--text-accent:var(--color-brand-primary);--status-success:#22c55e;--status-warn:#f59e0b;--status-error:#ef4444;--status-info:#3b82f6;--gradient-accent:linear-gradient(135deg,var(--color-brand-primary) 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ease;--primary:var(--color-brand-primary);--primary-dark:var(--color-brand-primary-alt);--primary-light:#60a5fa;--secondary:var(--color-brand-secondary);--accent:var(--color-brand-accent);--brand-primary:var(--color-brand-primary);--surface-primary:var(--bg-surface);--border-subtle:var(--border);--shadow-subtle:var(--shadow-sm);--success-color:var(--status-success);--warning-color:var(--status-warn);--info-color:var(--status-info);--error-color:var(--status-error)}html[data-theme=light]{--gray-50:#ffffff;--gray-100:#f8fafc;--gray-200:#eef2f6;--gray-300:#d2dae3;--gray-400:#a6b1bc;--gray-500:#7b8794;--gray-600:#5a6571;--gray-700:#404a53;--gray-800:#2c343b;--gray-850:#242b31;--gray-900:#1d2328;--gray-950:#14181c;--bg-body:var(--gray-100);--bg-surface:var(--gray-50);--bg-elevated:#f1f5f9;--bg-overlay:rgba(255,255,255,0.7);--bg-accent-faint:linear-gradient(135deg,rgba(79,70,229,0.08),rgba(6,182,212,0.08));--border:#d5dde5;--border-soft:#e2e8ef;--border-strong:#b9c3cc;--focus-ring:#2563eb;--text-primary:#1b2430;--text-secondary:#546173;--text-muted:#6b7785;--text-inverse:#ffffff;--text-accent:var(--color-brand-primary);--shadow-sm:0 1px 2px rgba(0,0,0,0.06);--shadow-md:0 4px 12px -2px rgba(0,0,0,0.1),0 0 0 1px rgba(0,0,0,0.04);--shadow-lg:0 10px 28px -6px rgba(0,0,0,0.15),0 0 0 1px rgba(0,0,0,0.05)}body,html{background:var(--bg-body)}.theme-surface,body,html{color:var(--text-primary)}.theme-surface{background:var(--bg-surface)}.theme-elevated{background:var(--bg-elevated);box-shadow:var(--shadow-md)}.theme-border{border:1px solid var(--border)}.theme-gradient-accent{background:var(--gradient-accent);color:#fff}.theme-transition *{transition:background-color var(--transition-normal),color var(--transition-normal),border-color var(--transition-normal)}