:root{--primary: #6366f1;--primary-light: #818cf8;--primary-dark: #4f46e5;--secondary: #10b981;--accent: #f59e0b;--danger: #ef4444;--success: #22c55e;--bg-primary: #0f0f1a;--bg-secondary: #1a1a2e;--bg-card: #16213e;--bg-hover: #1f2937;--text-primary: #f8fafc;--text-secondary: #94a3b8;--text-muted: #64748b;--gradient-primary: linear-gradient(135deg, #6366f1 0%, #8b5cf6 100%);--gradient-success: linear-gradient(135deg, #10b981 0%, #34d399 100%);--gradient-accent: linear-gradient(135deg, #f59e0b 0%, #fbbf24 100%);--gradient-card: linear-gradient(145deg, #1a1a2e 0%, #16213e 100%);--shadow-sm: 0 2px 8px rgba(0, 0, 0, .3);--shadow-md: 0 4px 16px rgba(0, 0, 0, .4);--shadow-lg: 0 8px 32px rgba(0, 0, 0, .5);--shadow-glow: 0 0 20px rgba(99, 102, 241, .3);--spacing-xs: .25rem;--spacing-sm: .5rem;--spacing-md: 1rem;--spacing-lg: 1.5rem;--spacing-xl: 2rem;--radius-sm: 8px;--radius-md: 12px;--radius-lg: 16px;--radius-full: 9999px;--font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif}*{margin:0;padding:0;box-sizing:border-box}html{font-size:16px;-webkit-text-size-adjust:100%}body{font-family:var(--font-family);background:var(--bg-primary);color:var(--text-primary);min-height:100vh;line-height:1.6;overflow-x:hidden}#root{min-height:100vh;display:flex;flex-direction:column}.app{display:flex;flex-direction:column;min-height:100vh;padding-bottom:70px}.main-content{flex:1;padding:var(--spacing-md);padding-top:60px;max-width:100%;overflow-x:hidden}.header{position:fixed;top:0;left:0;right:0;height:56px;background:var(--bg-secondary);border-bottom:1px solid rgba(255,255,255,.1);display:flex;align-items:center;justify-content:center;z-index:100;-webkit-backdrop-filter:blur(10px);backdrop-filter:blur(10px)}.header h1{font-size:1.1rem;font-weight:600;background:var(--gradient-primary);-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text}.nav{position:fixed;bottom:0;left:0;right:0;height:65px;background:var(--bg-secondary);border-top:1px solid rgba(255,255,255,.1);display:flex;justify-content:space-around;align-items:center;z-index:100;padding-bottom:env(safe-area-inset-bottom)}.nav-item{display:flex;flex-direction:column;align-items:center;gap:4px;padding:var(--spacing-sm);color:var(--text-muted);text-decoration:none;font-size:.7rem;transition:all .3s ease;cursor:pointer;border:none;background:none;min-width:60px}.nav-item.active{color:var(--primary)}.nav-item:active{transform:scale(.95)}.nav-icon{font-size:1.4rem}.card{background:var(--gradient-card);border-radius:var(--radius-md);padding:var(--spacing-lg);margin-bottom:var(--spacing-md);border:1px solid rgba(255,255,255,.05);box-shadow:var(--shadow-md);transition:all .3s ease}.card:hover{transform:translateY(-2px);box-shadow:var(--shadow-lg)}.card-title{font-size:1rem;font-weight:600;margin-bottom:var(--spacing-sm);color:var(--text-primary)}.card-content{font-size:.9rem;color:var(--text-secondary);line-height:1.7}.btn{padding:var(--spacing-md) var(--spacing-lg);border-radius:var(--radius-md);font-size:1rem;font-weight:600;border:none;cursor:pointer;transition:all .3s ease;display:inline-flex;align-items:center;justify-content:center;gap:var(--spacing-sm);min-height:48px;touch-action:manipulation}.btn-primary{background:var(--gradient-primary);color:#fff;box-shadow:var(--shadow-sm)}.btn-primary:active{transform:scale(.98);box-shadow:var(--shadow-glow)}.btn-secondary{background:var(--bg-hover);color:var(--text-primary);border:1px solid rgba(255,255,255,.1)}.btn-success{background:var(--gradient-success);color:#fff}.btn-block{width:100%}.btn-sm{padding:var(--spacing-sm) var(--spacing-md);font-size:.875rem;min-height:36px}.options{display:flex;flex-direction:column;gap:var(--spacing-sm)}.option{padding:var(--spacing-md);background:var(--bg-hover);border-radius:var(--radius-sm);border:2px solid transparent;cursor:pointer;transition:all .3s ease;font-size:.95rem;color:var(--text-primary);text-align:left}.option:active{transform:scale(.98)}.option.selected{border-color:var(--primary);background:#6366f126}.option.correct{border-color:var(--success);background:#22c55e26}.option.wrong{border-color:var(--danger);background:#ef444426}.input{width:100%;padding:var(--spacing-md);background:var(--bg-hover);border:2px solid rgba(255,255,255,.1);border-radius:var(--radius-sm);color:var(--text-primary);font-size:1rem;transition:all .3s ease}.input:focus{outline:none;border-color:var(--primary);box-shadow:var(--shadow-glow)}.input::placeholder{color:var(--text-muted)}.progress-container{margin-bottom:var(--spacing-lg)}.progress-label{display:flex;justify-content:space-between;margin-bottom:var(--spacing-xs);font-size:.85rem;color:var(--text-secondary)}.progress-bar{height:8px;background:var(--bg-hover);border-radius:var(--radius-full);overflow:hidden}.progress-fill{height:100%;background:var(--gradient-primary);border-radius:var(--radius-full);transition:width .5s ease}.tag{display:inline-block;padding:4px 12px;border-radius:var(--radius-full);font-size:.75rem;font-weight:600}.tag-primary{background:#6366f133;color:var(--primary-light)}.tag-success{background:#22c55e33;color:var(--success)}.tag-danger{background:#ef444433;color:var(--danger)}.tag-accent{background:#f59e0b33;color:var(--accent)}.chapter-tabs{display:flex;gap:var(--spacing-sm);overflow-x:auto;padding-bottom:var(--spacing-sm);margin-bottom:var(--spacing-md);-webkit-overflow-scrolling:touch}.chapter-tabs::-webkit-scrollbar{display:none}.chapter-tab{padding:var(--spacing-sm) var(--spacing-md);background:var(--bg-hover);border-radius:var(--radius-full);font-size:.85rem;white-space:nowrap;cursor:pointer;border:none;color:var(--text-secondary);transition:all .3s ease}.chapter-tab.active{background:var(--gradient-primary);color:#fff}.question-card{background:var(--gradient-card);border-radius:var(--radius-lg);padding:var(--spacing-lg);margin-bottom:var(--spacing-md);border:1px solid rgba(255,255,255,.05)}.question-header{display:flex;justify-content:space-between;align-items:center;margin-bottom:var(--spacing-md)}.question-number{font-size:.85rem;color:var(--text-muted)}.question-text{font-size:1rem;line-height:1.8;margin-bottom:var(--spacing-lg);color:var(--text-primary)}.answer-section{padding-top:var(--spacing-md);border-top:1px solid rgba(255,255,255,.1);margin-top:var(--spacing-md)}.answer-label{font-size:.85rem;color:var(--text-muted);margin-bottom:var(--spacing-xs)}.answer-text{font-size:1rem;color:var(--success);font-weight:600}.flashcard{background:var(--gradient-card);border-radius:var(--radius-lg);min-height:250px;display:flex;flex-direction:column;justify-content:center;align-items:center;padding:var(--spacing-xl);text-align:center;cursor:pointer;transition:all .5s ease;perspective:1000px;border:1px solid rgba(255,255,255,.05)}.flashcard.flipped{background:linear-gradient(145deg,#1e3a5f,#16213e)}.flashcard-content{font-size:1.1rem;line-height:1.8}.flashcard-hint{font-size:.85rem;color:var(--text-muted);margin-top:var(--spacing-md)}.timer{display:flex;align-items:center;gap:var(--spacing-sm);font-size:1.2rem;font-weight:600;color:var(--accent)}.timer-icon{font-size:1.4rem}.score-display{text-align:center;padding:var(--spacing-xl)}.score-number{font-size:4rem;font-weight:700;background:var(--gradient-primary);-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text}.score-label{font-size:1.2rem;color:var(--text-secondary);margin-top:var(--spacing-sm)}.fill-blank{display:inline-block;min-width:100px;border-bottom:2px solid var(--primary);padding:4px 8px;margin:0 4px;text-align:center;color:var(--primary-light);font-weight:600}.fill-blank-input{background:transparent;border:none;border-bottom:2px solid var(--primary);padding:4px 8px;min-width:120px;color:var(--text-primary);font-size:1rem;text-align:center}.fill-blank-input:focus{outline:none;border-color:var(--primary-light)}@keyframes fadeIn{0%{opacity:0;transform:translateY(10px)}to{opacity:1;transform:translateY(0)}}@keyframes pulse{0%,to{transform:scale(1)}50%{transform:scale(1.02)}}@keyframes slideUp{0%{opacity:0;transform:translateY(20px)}to{opacity:1;transform:translateY(0)}}.animate-fadeIn{animation:fadeIn .4s ease}.animate-pulse{animation:pulse 2s infinite}.animate-slideUp{animation:slideUp .5s ease}.text-center{text-align:center}.text-left{text-align:left}.text-muted{color:var(--text-muted)}.text-success{color:var(--success)}.text-danger{color:var(--danger)}.mt-sm{margin-top:var(--spacing-sm)}.mt-md{margin-top:var(--spacing-md)}.mt-lg{margin-top:var(--spacing-lg)}.mb-sm{margin-bottom:var(--spacing-sm)}.mb-md{margin-bottom:var(--spacing-md)}.mb-lg{margin-bottom:var(--spacing-lg)}.flex{display:flex}.flex-col{flex-direction:column}.items-center{align-items:center}.justify-between{justify-content:space-between}.gap-sm{gap:var(--spacing-sm)}.gap-md{gap:var(--spacing-md)}.empty-state{text-align:center;padding:var(--spacing-xl) var(--spacing-lg);color:var(--text-muted)}.empty-state-icon{font-size:3rem;margin-bottom:var(--spacing-md);opacity:.5}.knowledge-card{background:var(--gradient-card);border-radius:var(--radius-md);padding:var(--spacing-lg);margin-bottom:var(--spacing-md);border-left:4px solid var(--primary);transition:all .3s ease}.knowledge-card.important{border-left-color:var(--danger)}.knowledge-card-header{display:flex;justify-content:space-between;align-items:flex-start;margin-bottom:var(--spacing-sm)}.knowledge-card-title{font-size:1rem;font-weight:600;color:var(--text-primary);flex:1}.knowledge-card-content{font-size:.9rem;color:var(--text-secondary);line-height:1.7;display:none}.knowledge-card.expanded .knowledge-card-content{display:block;margin-top:var(--spacing-md);padding-top:var(--spacing-md);border-top:1px solid rgba(255,255,255,.1)}.expand-icon{font-size:1.2rem;color:var(--text-muted);transition:transform .3s ease}.knowledge-card.expanded .expand-icon{transform:rotate(180deg)}.actions-bar{display:flex;gap:var(--spacing-sm);margin-top:var(--spacing-lg)}.actions-bar .btn{flex:1}@media (min-width: 768px){.main-content{max-width:600px;margin:0 auto;padding:var(--spacing-lg);padding-top:70px}.nav{max-width:600px;left:50%;transform:translate(-50%);border-radius:var(--radius-lg) var(--radius-lg) 0 0}}