:root{--color-bg-primary: #f0f4f9;--color-bg-secondary: #ffffff;--color-bg-card: #ffffff;--color-text-primary: #1a1a2e;--color-text-secondary: #6b7280;--color-text-muted: #9ca3af;--color-primary: #4a90d9;--color-primary-hover: #3a7bc8;--color-primary-light: rgba(74, 144, 217, .1);--color-accent-orange: linear-gradient(135deg, #ff7e5f 0%, #feb47b 100%);--color-accent-red: linear-gradient(135deg, #ff6b6b 0%, #ff8e8e 100%);--color-accent-yellow: linear-gradient(135deg, #f6d365 0%, #fda085 100%);--color-success: #10b981;--color-error: #ef4444;--color-warning: #f59e0b;--color-wordcloud-primary: #5a8bb8;--color-wordcloud-secondary: #8ab4d8;--color-wordcloud-accent: #3d6a8f;--color-wordcloud-highlight: #e74c3c;--spacing-xs: 4px;--spacing-sm: 8px;--spacing-md: 16px;--spacing-lg: 24px;--spacing-xl: 32px;--spacing-2xl: 48px;--radius-sm: 8px;--radius-md: 12px;--radius-lg: 16px;--radius-xl: 24px;--radius-full: 9999px;--shadow-sm: 0 1px 3px rgba(0, 0, 0, .08);--shadow-md: 0 4px 12px rgba(0, 0, 0, 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var(--spacing-lg);border-radius:var(--radius-full);font-size:var(--font-size-md);font-weight:600;transition:all var(--transition-normal)}.btn-primary{background:var(--color-primary);color:#fff;padding:var(--spacing-md) var(--spacing-2xl);font-size:var(--font-size-lg);box-shadow:var(--shadow-md)}.btn-primary:hover{background:var(--color-primary-hover);transform:translateY(-2px);box-shadow:var(--shadow-lg)}.btn-primary:active{transform:translateY(0)}.card{background:var(--color-bg-card);border-radius:var(--radius-md);box-shadow:var(--shadow-sm);padding:var(--spacing-md)}@keyframes fadeIn{0%{opacity:0;transform:translateY(10px)}to{opacity:1;transform:translateY(0)}}@keyframes pulse{0%,to{transform:scale(1)}50%{transform:scale(1.05)}}@keyframes bounce{0%,to{transform:translateY(0)}50%{transform:translateY(-10px)}}.animate-fadeIn{animation:fadeIn var(--transition-normal) ease-out}@media(max-width:1024px){:root{--sidebar-width: 240px}}@media(max-width:768px){:root{--sidebar-width: 0}.main-content{margin-left:0;padding:var(--spacing-md);padding-bottom:80px}}::-webkit-scrollbar{width:8px;height:8px}::-webkit-scrollbar-track{background:transparent}::-webkit-scrollbar-thumb{background:var(--color-text-muted);border-radius:var(--radius-full)}::-webkit-scrollbar-thumb:hover{background:var(--color-text-secondary)}.sidebar{position:fixed;left:0;top:0;width:var(--sidebar-width);height:100vh;background:var(--color-bg-secondary);padding:var(--spacing-lg);display:flex;flex-direction:column;box-shadow:var(--shadow-md);z-index:100;overflow-y:auto}.sidebar-header{display:flex;align-items:center;justify-content:space-between;margin-bottom:var(--spacing-lg);padding-bottom:var(--spacing-md);border-bottom:1px solid rgba(0,0,0,.06)}.sidebar-title{font-size:var(--font-size-lg);font-weight:700;color:var(--color-text-primary)}.sidebar-action{font-size:var(--font-size-sm);color:var(--color-primary);cursor:pointer;transition:opacity var(--transition-fast)}.sidebar-action:hover{opacity:.8}.wordbook-list{display:flex;flex-direction:column;gap:var(--spacing-md);flex:1}.wordbook-card{position:relative;border-radius:var(--radius-md);padding:var(--spacing-md);color:#fff;cursor:pointer;transition:all var(--transition-normal);overflow:hidden}.wordbook-card:before{content:"";position:absolute;inset:0;background:#ffffff1a;opacity:0;transition:opacity var(--transition-fast)}.wordbook-card:hover{transform:translateY(-4px);box-shadow:var(--shadow-lg)}.wordbook-card:hover:before{opacity:1}.wordbook-card.active{box-shadow:0 0 0 3px #ffffff80,var(--shadow-lg);transform:translateY(-4px)}.wordbook-card--orange{background:var(--color-accent-orange)}.wordbook-card--red{background:var(--color-accent-red)}.wordbook-card--yellow{background:var(--color-accent-yellow)}.wordbook-badge{position:absolute;top:var(--spacing-sm);right:var(--spacing-sm);background:#ffffffe6;color:var(--color-primary);font-size:var(--font-size-xs);padding:2px 8px;border-radius:var(--radius-full);font-weight:600}.wordbook-title{font-size:var(--font-size-md);font-weight:700;margin-bottom:var(--spacing-xs)}.wordbook-subtitle{font-size:var(--font-size-sm);opacity:.9;margin-bottom:var(--spacing-md)}.wordbook-meta{display:flex;align-items:center;gap:var(--spacing-md);font-size:var(--font-size-xs);opacity:.85}.wordbook-meta-item{display:flex;align-items:center;gap:var(--spacing-xs)}.wordbook-progress{display:flex;align-items:center;gap:var(--spacing-xs);margin-left:auto;background:#fff3;padding:2px 8px;border-radius:var(--radius-full)}@media(max-width:768px){.sidebar{position:fixed;inset:auto 0 0;width:100%;height:auto;max-height:70vh;border-radius:var(--radius-lg) var(--radius-lg) 0 0;transform:translateY(calc(100% - 60px));transition:transform var(--transition-normal);padding-bottom:env(safe-area-inset-bottom,20px)}.sidebar.expanded{transform:translateY(0)}.sidebar-handle{display:flex;align-items:center;justify-content:center;padding:var(--spacing-sm);cursor:pointer}.sidebar-handle:before{content:"";width:40px;height:4px;background:var(--color-text-muted);border-radius:var(--radius-full)}.wordbook-list{flex-direction:row;overflow-x:auto;padding-bottom:var(--spacing-sm);-webkit-overflow-scrolling:touch}.wordbook-card{min-width:200px;flex-shrink:0}}@media(min-width:769px){.sidebar-handle{display:none}}.wordcloud-container{flex:1;display:flex;flex-direction:column;background:var(--color-bg-secondary);border-radius:var(--radius-lg);box-shadow:var(--shadow-md);overflow:hidden}.wordcloud-header{display:flex;align-items:center;justify-content:space-between;padding:var(--spacing-md) var(--spacing-lg);border-bottom:1px solid rgba(0,0,0,.06)}.wordcloud-title{font-size:var(--font-size-lg);font-weight:600;color:var(--color-text-primary)}.wordcloud-progress{display:flex;align-items:center;gap:var(--spacing-sm);font-size:var(--font-size-sm);color:var(--color-text-secondary)}.wordcloud-level{font-size:var(--font-size-sm);color:var(--color-text-secondary)}.wordcloud-content{flex:1;display:flex;align-items:center;justify-content:center;padding:var(--spacing-lg);position:relative;min-height:400px}.wordcloud-svg{width:100%;height:100%;min-height:400px}.wordcloud-word{cursor:pointer;transition:all var(--transition-fast);font-family:var(--font-family)}.wordcloud-word:hover{filter:brightness(1.2)}.wordcloud-word.selected{filter:brightness(1.3);stroke:var(--color-wordcloud-highlight);stroke-width:1px}.wordcloud-word.center-word{font-weight:700}.wordcloud-footer{display:flex;align-items:center;justify-content:center;padding:var(--spacing-lg);border-top:1px solid rgba(0,0,0,.06)}.word-popup-overlay{position:fixed;inset:0;background:#0006;display:flex;align-items:center;justify-content:center;z-index:1000;animation:fadeIn var(--transition-fast) ease-out}.word-popup{background:var(--color-bg-secondary);border-radius:var(--radius-lg);padding:var(--spacing-xl);min-width:300px;max-width:90vw;box-shadow:var(--shadow-xl);animation:popupSlideIn var(--transition-normal) ease-out}@keyframes popupSlideIn{0%{opacity:0;transform:translateY(20px) scale(.95)}to{opacity:1;transform:translateY(0) scale(1)}}.word-popup-header{display:flex;align-items:flex-start;justify-content:space-between;margin-bottom:var(--spacing-md)}.word-popup-word{font-size:var(--font-size-3xl);font-weight:700;color:var(--color-wordcloud-primary)}.word-popup-phonetic{font-size:var(--font-size-md);color:var(--color-text-secondary);margin-top:var(--spacing-xs)}.word-popup-close{font-size:var(--font-size-xl);color:var(--color-text-muted);cursor:pointer;padding:var(--spacing-xs);line-height:1;transition:color var(--transition-fast)}.word-popup-close:hover{color:var(--color-text-primary)}.word-popup-meaning{font-size:var(--font-size-lg);color:var(--color-text-primary);margin-bottom:var(--spacing-lg);padding:var(--spacing-md);background:var(--color-primary-light);border-radius:var(--radius-md)}.word-popup-actions{display:flex;gap:var(--spacing-md)}.word-popup-btn{flex:1;display:flex;align-items:center;justify-content:center;gap:var(--spacing-sm);padding:var(--spacing-sm) var(--spacing-md);border-radius:var(--radius-md);font-size:var(--font-size-sm);font-weight:500;transition:all var(--transition-fast)}.word-popup-btn--primary{background:var(--color-primary);color:#fff}.word-popup-btn--primary:hover{background:var(--color-primary-hover)}.word-popup-btn--secondary{background:var(--color-bg-primary);color:var(--color-text-primary)}.word-popup-btn--secondary:hover{background:#00000014}@media(max-width:768px){.wordcloud-container{border-radius:var(--radius-md)}.wordcloud-header{flex-direction:column;align-items:flex-start;gap:var(--spacing-sm)}.wordcloud-content{min-height:300px;padding:var(--spacing-md)}.word-popup{margin:var(--spacing-md);padding:var(--spacing-lg)}}.quiz-container{flex:1;display:flex;flex-direction:column;background:var(--color-bg-secondary);border-radius:var(--radius-lg);box-shadow:var(--shadow-md);overflow:hidden;animation:fadeIn var(--transition-normal)}.quiz-header{display:flex;align-items:center;justify-content:space-between;padding:var(--spacing-md) var(--spacing-lg);border-bottom:1px solid rgba(0,0,0,.06)}.quiz-back{display:flex;align-items:center;gap:var(--spacing-sm);font-size:var(--font-size-md);color:var(--color-text-secondary);cursor:pointer;transition:color var(--transition-fast)}.quiz-back:hover{color:var(--color-primary)}.quiz-progress{display:flex;align-items:center;gap:var(--spacing-md)}.quiz-progress-text{font-size:var(--font-size-sm);color:var(--color-text-secondary)}.quiz-progress-bar{width:200px;height:8px;background:var(--color-bg-primary);border-radius:var(--radius-full);overflow:hidden}.quiz-progress-fill{height:100%;background:var(--color-primary);border-radius:var(--radius-full);transition:width var(--transition-normal)}.quiz-type-badge{background:var(--color-primary-light);color:var(--color-primary);font-size:var(--font-size-xs);padding:var(--spacing-xs) var(--spacing-sm);border-radius:var(--radius-full);font-weight:600}.quiz-content{flex:1;display:flex;flex-direction:column;align-items:center;justify-content:center;padding:var(--spacing-2xl);gap:var(--spacing-xl)}.quiz-question{text-align:center;max-width:600px}.quiz-question-word{font-size:var(--font-size-3xl);font-weight:700;color:var(--color-wordcloud-primary);margin-bottom:var(--spacing-sm)}.quiz-question-phonetic{font-size:var(--font-size-md);color:var(--color-text-secondary)}.quiz-question-meaning{font-size:var(--font-size-2xl);color:var(--color-text-primary);font-weight:600}.quiz-question-prompt{font-size:var(--font-size-md);color:var(--color-text-secondary);margin-top:var(--spacing-sm)}.quiz-audio-btn{width:80px;height:80px;border-radius:50%;background:var(--color-primary);color:#fff;font-size:32px;display:flex;align-items:center;justify-content:center;cursor:pointer;transition:all var(--transition-normal);box-shadow:var(--shadow-md)}.quiz-audio-btn:hover{transform:scale(1.1);box-shadow:var(--shadow-lg)}.quiz-audio-btn:active{transform:scale(.95)}.quiz-options{display:grid;grid-template-columns:repeat(2,1fr);gap:var(--spacing-md);width:100%;max-width:600px}.quiz-option{padding:var(--spacing-lg);background:var(--color-bg-primary);border-radius:var(--radius-md);font-size:var(--font-size-md);text-align:center;cursor:pointer;transition:all var(--transition-fast);border:2px solid transparent}.quiz-option:hover,.quiz-option.selected{background:var(--color-primary-light);border-color:var(--color-primary)}.quiz-option.correct{background:#10b9811a;border-color:var(--color-success);color:var(--color-success)}.quiz-option.incorrect{background:#ef44441a;border-color:var(--color-error);color:var(--color-error)}.quiz-input-container{width:100%;max-width:400px}.quiz-input{width:100%;padding:var(--spacing-md) var(--spacing-lg);font-size:var(--font-size-xl);text-align:center;border:2px solid var(--color-text-muted);border-radius:var(--radius-md);outline:none;transition:border-color var(--transition-fast)}.quiz-input:focus{border-color:var(--color-primary)}.quiz-input.correct{border-color:var(--color-success);background:#10b9811a}.quiz-input.incorrect{border-color:var(--color-error);background:#ef44441a}.quiz-submit-btn{margin-top:var(--spacing-md)}.quiz-mixed-container{display:flex;gap:var(--spacing-xl);width:100%;max-width:800px}.quiz-mixed-words,.quiz-mixed-meanings{flex:1;display:flex;flex-direction:column;gap:var(--spacing-sm)}.quiz-mixed-label{font-size:var(--font-size-sm);color:var(--color-text-secondary);font-weight:600;margin-bottom:var(--spacing-xs)}.quiz-mixed-item{padding:var(--spacing-md);background:var(--color-bg-primary);border-radius:var(--radius-md);cursor:pointer;transition:all var(--transition-fast);border:2px solid transparent}.quiz-mixed-item:hover{background:var(--color-primary-light)}.quiz-mixed-item.selected{border-color:var(--color-primary);background:var(--color-primary-light)}.quiz-mixed-item.matched{border-color:var(--color-success);background:#10b9811a;pointer-events:none}.quiz-footer{display:flex;align-items:center;justify-content:center;padding:var(--spacing-lg);border-top:1px solid rgba(0,0,0,.06);gap:var(--spacing-md)}.quiz-result{flex:1;display:flex;flex-direction:column;align-items:center;justify-content:center;padding:var(--spacing-2xl);text-align:center}.quiz-result-score{font-size:72px;font-weight:700;color:var(--color-primary);margin-bottom:var(--spacing-md)}.quiz-result-label{font-size:var(--font-size-lg);color:var(--color-text-secondary);margin-bottom:var(--spacing-xl)}.quiz-result-stats{display:flex;gap:var(--spacing-xl);margin-bottom:var(--spacing-2xl)}.quiz-result-stat{text-align:center}.quiz-result-stat-value{font-size:var(--font-size-2xl);font-weight:700}.quiz-result-stat-value.correct{color:var(--color-success)}.quiz-result-stat-value.incorrect{color:var(--color-error)}.quiz-result-stat-label{font-size:var(--font-size-sm);color:var(--color-text-secondary)}.quiz-result-actions{display:flex;gap:var(--spacing-md)}@media(max-width:768px){.quiz-content{padding:var(--spacing-lg)}.quiz-options{grid-template-columns:1fr}.quiz-progress-bar{width:100px}.quiz-mixed-container{flex-direction:column}.quiz-question-word{font-size:var(--font-size-2xl)}.quiz-result-score{font-size:56px}}.loading-container{flex:1;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:var(--spacing-md)}.loading-spinner{width:48px;height:48px;border:4px solid var(--color-bg-primary);border-top-color:var(--color-primary);border-radius:50%;animation:spin 1s linear infinite}@keyframes spin{to{transform:rotate(360deg)}}.loading-text{font-size:var(--font-size-md);color:var(--color-text-secondary)}.empty-state{flex:1;display:flex;flex-direction:column;align-items:center;justify-content:center;text-align:center;padding:var(--spacing-2xl)}.empty-state-icon{font-size:64px;margin-bottom:var(--spacing-lg)}.empty-state-title{font-size:var(--font-size-xl);font-weight:600;color:var(--color-text-primary);margin-bottom:var(--spacing-sm)}.empty-state-description{font-size:var(--font-size-md);color:var(--color-text-secondary)}