:root{--primary: #6366f1;--primary-hover: #4f46e5;--primary-light: #e0e7ff;--success: #22c55e;--success-hover: #16a34a;--warning: #f59e0b;--danger: #ef4444;--danger-hover: #dc2626;--bg: #f8fafc;--bg-card: #ffffff;--bg-secondary: #f1f5f9;--text: #1e293b;--text-secondary: #64748b;--text-muted: #94a3b8;--border: #e2e8f0;--border-hover: #cbd5e1;--shadow-sm: 0 1px 2px rgba(0, 0, 0, .05);--shadow: 0 4px 6px -1px rgba(0, 0, 0, .1);--shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, .1);--radius: 8px;--radius-lg: 12px}*{box-sizing:border-box;margin:0;padding:0}body{font-family:Inter,-apple-system,BlinkMacSystemFont,sans-serif;background:var(--bg);color:var(--text);line-height:1.5;min-height:100vh}#app{max-width:800px;margin:0 auto;padding:0 16px}.header{display:flex;justify-content:space-between;align-items:center;padding:16px 0;border-bottom:1px solid var(--border);margin-bottom:24px}.logo{font-size:1.25rem;font-weight:700;color:var(--primary)}.loading{text-align:center;padding:48px;color:var(--text-secondary)}.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;padding:10px 20px;font-size:.875rem;font-weight:500;border-radius:var(--radius);border:none;cursor:pointer;transition:all .15s ease}.btn-primary{background:var(--primary);color:#fff}.btn-primary:hover{background:var(--primary-hover)}.btn-secondary{background:var(--bg-secondary);color:var(--text);border:1px solid var(--border)}.btn-secondary:hover{background:var(--border)}.btn-success{background:var(--success);color:#fff}.btn-success:hover{background:var(--success-hover)}.btn-danger{background:var(--danger);color:#fff}.btn-danger:hover{background:var(--danger-hover)}.btn-lg{padding:14px 28px;font-size:1rem}.btn-block{width:100%}.card{background:var(--bg-card);border-radius:var(--radius-lg);box-shadow:var(--shadow);padding:24px}.login-view{display:flex;flex-direction:column;align-items:center;justify-content:center;min-height:60vh;text-align:center}.login-view h2{font-size:1.5rem;margin-bottom:8px}.login-view p{color:var(--text-secondary);margin-bottom:32px}.oauth-buttons{display:flex;flex-direction:column;gap:12px;width:100%;max-width:300px}.oauth-btn{display:flex;align-items:center;justify-content:center;gap:12px;padding:12px 24px;font-size:.875rem;font-weight:500;border-radius:var(--radius);border:1px solid var(--border);background:#fff;cursor:pointer;transition:all .15s ease}.oauth-btn:hover{background:var(--bg-secondary);border-color:var(--border-hover)}.oauth-btn svg{width:20px;height:20px}.deck-list{display:flex;flex-direction:column;gap:12px}.deck-item{display:flex;justify-content:space-between;align-items:center;padding:16px 20px;background:var(--bg-card);border-radius:var(--radius);border:1px solid var(--border);cursor:pointer;transition:all .15s ease}.deck-item:hover{border-color:var(--primary);box-shadow:var(--shadow)}.deck-info h3{font-size:1rem;font-weight:600;margin-bottom:4px}.deck-info p{font-size:.875rem;color:var(--text-secondary)}.deck-stats{display:flex;gap:16px;align-items:center}.deck-stat{text-align:center}.deck-stat-value{font-size:1.25rem;font-weight:700;color:var(--primary)}.deck-stat-label{font-size:.75rem;color:var(--text-muted)}.user-menu{display:flex;align-items:center;gap:12px}.user-avatar{width:32px;height:32px;border-radius:50%;background:var(--primary-light)}.user-name{font-size:.875rem;font-weight:500}.user-dropdown{position:relative}.user-dropdown-content{position:absolute;top:100%;right:0;margin-top:8px;background:#fff;border-radius:var(--radius);box-shadow:var(--shadow-lg);border:1px solid var(--border);min-width:160px;display:none;z-index:100}.user-dropdown-content.show{display:block}.user-dropdown-item{display:block;padding:10px 16px;font-size:.875rem;color:var(--text);text-decoration:none;cursor:pointer}.user-dropdown-item:hover{background:var(--bg-secondary)}.progress-bar{height:4px;background:var(--bg-secondary);border-radius:2px;overflow:hidden;margin-bottom:16px}.progress-bar-fill{height:100%;background:var(--primary);transition:width .3s ease}.stats-overview{display:grid;grid-template-columns:repeat(auto-fit,minmax(120px,1fr));gap:16px;margin-bottom:24px}.stat-card{background:var(--bg-card);border-radius:var(--radius);padding:16px;text-align:center;border:1px solid var(--border)}.stat-value{font-size:1.5rem;font-weight:700;color:var(--primary)}.stat-label{font-size:.75rem;color:var(--text-muted);margin-top:4px}.overall-stats{display:grid;grid-template-columns:repeat(4,1fr);gap:12px;margin-bottom:24px;padding:16px;background:var(--bg-card);border-radius:var(--radius);border:1px solid var(--border)}.overall-stat{text-align:center;padding:8px}.overall-stat-value{font-size:1.75rem;font-weight:700;color:var(--primary);line-height:1}.overall-stat-label{font-size:.75rem;color:var(--text-muted);margin-top:6px;text-transform:uppercase;letter-spacing:.5px}.progress-section{margin-top:48px;padding-top:24px;border-top:1px solid var(--border)}.progress-section h3{font-size:1.125rem;font-weight:600;margin-bottom:20px}.chart-container{background:var(--bg-card);border-radius:var(--radius);padding:24px;border:1px solid var(--border)}.chart-bars{display:flex;align-items:flex-end;justify-content:space-around;gap:8px;height:200px}.chart-bar-wrapper{flex:1;display:flex;flex-direction:column;align-items:center;height:100%;justify-content:flex-end}.chart-bar{width:100%;min-height:20px;background:linear-gradient(135deg,var(--primary) 0%,var(--primary-hover) 100%);border-radius:4px 4px 0 0;display:flex;align-items:flex-start;justify-content:center;padding-top:6px;transition:all .3s ease;position:relative}.chart-bar:hover{opacity:.8;transform:translateY(-2px)}.chart-bar-value{font-size:.75rem;font-weight:600;color:#fff}.chart-bar-label{font-size:.75rem;color:var(--text-muted);margin-top:8px;text-align:center}.study-complete{text-align:center;padding:48px 24px}.study-complete h2{font-size:1.5rem;margin-bottom:8px}.study-complete p{color:var(--text-secondary);margin-bottom:24px}.study-results{display:flex;justify-content:center;gap:32px;margin-bottom:32px}.study-result{text-align:center}.study-result-value{font-size:2rem;font-weight:700}.study-result-value.correct{color:var(--success)}.study-result-value.incorrect{color:var(--danger)}.study-result-label{font-size:.875rem;color:var(--text-muted)}.admin-nav{display:flex;gap:8px;margin-bottom:24px;border-bottom:1px solid var(--border);padding-bottom:16px}.admin-nav-item{padding:8px 16px;font-size:.875rem;font-weight:500;color:var(--text-secondary);background:none;border:none;cursor:pointer;border-radius:var(--radius)}.admin-nav-item:hover{background:var(--bg-secondary)}.admin-nav-item.active{background:var(--primary-light);color:var(--primary)}.form-group{margin-bottom:16px}.form-label{display:block;font-size:.875rem;font-weight:500;margin-bottom:6px}.form-input{width:100%;padding:10px 12px;font-size:.875rem;border:1px solid var(--border);border-radius:var(--radius);transition:border-color .15s ease}.form-input:focus{outline:none;border-color:var(--primary)}.form-help{font-size:.75rem;color:var(--text-muted);margin-top:4px}.table-container{overflow-x:auto}table{width:100%;border-collapse:collapse}th,td{padding:12px;text-align:left;border-bottom:1px solid var(--border)}th{font-size:.75rem;font-weight:600;color:var(--text-muted);text-transform:uppercase}td{font-size:.875rem}tr:hover{background:var(--bg-secondary)}@media (max-width: 640px){.deck-item{flex-direction:column;align-items:flex-start;gap:12px}.deck-stats{width:100%;justify-content:space-around}.study-results{flex-direction:column;gap:16px}.overall-stats{grid-template-columns:repeat(2,1fr);gap:8px;padding:12px}.overall-stat{padding:4px}.overall-stat-value{font-size:1.5rem}.overall-stat-label{font-size:.625rem}.chart-bars{height:150px}.chart-bar-value{font-size:.625rem}}.study-view{display:flex;flex-direction:column;align-items:center;padding:24px 0}.study-header{width:100%;display:flex;justify-content:space-between;align-items:center;margin-bottom:24px}.study-header h2{font-size:1.125rem;font-weight:600}.study-progress{font-size:.875rem;color:var(--text-secondary)}.flashcard-container{perspective:1000px;width:100%;max-width:400px;height:300px;margin-bottom:32px}.flashcard{width:100%;height:100%;position:relative;transform-style:preserve-3d;transition:transform .6s cubic-bezier(.4,0,.2,1);cursor:pointer}.flashcard.flipped{transform:rotateY(180deg)}.flashcard-face{position:absolute;width:100%;height:100%;backface-visibility:hidden;display:flex;flex-direction:column;justify-content:center;align-items:center;padding:32px;background:var(--bg-card);border-radius:var(--radius-lg);box-shadow:var(--shadow-lg);border:1px solid var(--border)}.flashcard-front{background:linear-gradient(135deg,#667eea,#764ba2);color:#fff}.flashcard-back{transform:rotateY(180deg);background:var(--bg-card)}.flashcard-content{font-size:1.5rem;font-weight:600;text-align:center;word-break:break-word}.flashcard-hint{position:absolute;bottom:16px;font-size:.75rem;opacity:.7}.flashcard-example{margin-top:16px;padding-top:16px;border-top:1px solid var(--border);width:100%;text-align:center}.flashcard-example-native{font-size:.875rem;color:var(--text);font-style:italic;margin-bottom:4px}.flashcard-example-english{font-size:.75rem;color:var(--text-secondary)}.flashcard-meta{position:absolute;top:12px;right:12px;display:flex;gap:8px}.flashcard-badge{font-size:.625rem;font-weight:600;padding:2px 8px;border-radius:12px;background:var(--primary-light);color:var(--primary)}.rating-buttons{display:grid;grid-template-columns:repeat(3,1fr);gap:12px;width:100%;max-width:500px}.rating-btn{display:flex;flex-direction:column;align-items:center;gap:4px;padding:16px 12px;border:none;border-radius:var(--radius);cursor:pointer;transition:all .15s ease;font-weight:500}.rating-btn:disabled{opacity:.5;cursor:not-allowed}.rating-btn-again{background:#fef2f2;color:#dc2626}.rating-btn-again:hover:not(:disabled){background:#fee2e2}.rating-btn-hard{background:#fef3c7;color:#d97706}.rating-btn-hard:hover:not(:disabled){background:#fde68a}.rating-btn-easy{background:#dbeafe;color:#2563eb}.rating-btn-easy:hover:not(:disabled){background:#bfdbfe}.rating-label{font-size:.875rem;font-weight:600}.rating-desc{font-size:.625rem;opacity:.7;font-weight:400;text-align:center;line-height:1.2}.rating-interval{font-size:.625rem;opacity:.7;margin-top:2px}.empty-state{text-align:center;padding:48px 24px}.empty-state-icon{font-size:3rem;margin-bottom:16px}.empty-state h3{font-size:1.25rem;margin-bottom:8px}.empty-state p{color:var(--text-secondary);margin-bottom:24px}@keyframes slideIn{0%{opacity:0;transform:translateY(20px)}to{opacity:1;transform:translateY(0)}}.flashcard-container{animation:slideIn .3s ease}@media (hover: none){.flashcard:active{transform:scale(.98)}.flashcard.flipped:active{transform:rotateY(180deg) scale(.98)}}