:root{--bg-primary: #f7f7f8;--bg-secondary: #ffffff;--bg-tertiary: #eef2f7;--bg-hover: #f2f2f2;--bg-active: #e5e5e5;--text-primary: #1c1c1e;--text-secondary: #545458;--text-muted: #8a8a8e;--text-accent: #2563eb;--border-primary: #e5e5e5;--border-secondary: #d1d1d6;--border-focus: #2563eb;--success: #10b981;--error: #ef4444;--warning: #f59e0b;--border-radius: 10px;--border-radius-sm: 6px;--border-radius-lg: 14px;--spacing-xs: 4px;--spacing-sm: 8px;--spacing-md: 16px;--spacing-lg: 24px;--spacing-xl: 32px;--spacing-2xl: 48px;--shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, .03);--shadow-md: 0 4px 6px -1px rgba(0, 0, 0, .05), 0 2px 4px -1px rgba(0, 0, 0, .04);--shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, .07), 0 4px 6px -2px rgba(0, 0, 0, .04);--transition: all .2s ease-in-out;--transition-slow: all .35s ease}html[data-theme=light]{--bg-primary: #f7f7f8;--bg-secondary: #ffffff;--bg-tertiary: #eef2f7;--bg-hover: #f2f2f2;--bg-active: #e5e5e5;--text-primary: #1c1c1e;--text-secondary: #545458;--text-muted: #8a8a8e;--text-accent: #2563eb;--border-primary: #e5e5e5;--border-secondary: #d1d1d6;--border-focus: #2563eb}html[data-theme=dark]{--bg-primary: #1a1a1a;--bg-secondary: #2d2d2d;--bg-tertiary: #3a3a3a;--bg-hover: #404040;--bg-active: #4a4a4a;--text-primary: #ffffff;--text-secondary: #b0b0b0;--text-muted: #808080;--border-primary: #404040;--border-secondary: #505050}@media (max-width: 360px){header{padding:4px var(--spacing-md);min-height:48px}.logo h1{font-size:1rem;letter-spacing:.1px}.logo .logo-icon{width:20px;height:20px;flex-basis:20px}header .btn-secondary{padding:4px 6px;min-height:32px}}.loading-state{display:flex;flex-direction:column;align-items:center;justify-content:center;gap:12px;min-height:220px;background:var(--bg-secondary);border:1px solid var(--border-primary);border-radius:var(--border-radius);padding:var(--spacing-lg);color:var(--text-secondary)}.loading-state .spinner{width:32px;height:32px;border:3px solid var(--bg-tertiary);border-top-color:var(--text-accent);border-radius:50%;animation:spin .9s linear infinite}@keyframes spin{0%{transform:rotate(0)}to{transform:rotate(360deg)}}.loading-state.error-state{border-color:#ef444440}.loading-state .error-icon{color:var(--error);width:28px;height:28px}body{font-family:Inter,-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Helvetica,Arial,sans-serif;line-height:1.6;margin:0;padding:0;background:var(--bg-primary);color:var(--text-primary);font-size:16px;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale}main{max-width:1200px;margin:0 auto;padding:var(--spacing-lg)}.view{opacity:0;transform:translateY(6px);transition:var(--transition-slow)}.view[style*="display: block"],.view[style*="display: flex"],.view[style*="display: grid"]{opacity:1;transform:translateY(0)}.app-container{display:grid;grid-template-columns:260px 1fr;gap:0;align-items:start}.sidebar{position:sticky;top:72px;height:calc(100dvh - 72px);align-self:start;overflow-y:auto;display:flex;flex-direction:column}.sidebar .sidebar-inner{display:flex;flex-direction:column;min-height:100%}.sidebar-header{display:none;justify-content:space-between;align-items:center;padding:var(--spacing-md);border-bottom:1px solid var(--border-primary);background:var(--bg-secondary)}.sidebar-header h2{margin:0;font-size:1.1rem;font-weight:600;color:var(--text-primary)}.sidebar-close{background:none;border:none;padding:var(--spacing-xs);border-radius:var(--border-radius-sm);cursor:pointer;color:var(--text-secondary);transition:var(--transition);display:flex;align-items:center;justify-content:center;width:32px;height:32px}.sidebar-close:hover{background:var(--bg-hover);color:var(--text-primary)}.sidebar-nav{display:flex;flex-direction:column;gap:6px;padding:12px;flex-grow:1}.sidebar-nav a{text-decoration:none;color:var(--text-secondary);font-weight:500;padding:10px 12px;border-radius:var(--border-radius-sm);transition:var(--transition);display:flex;align-items:center;justify-content:space-between}.sidebar-nav a:hover{color:var(--text-primary);background-color:var(--bg-hover)}.sidebar-toggle{display:none;gap:6px;align-items:center;flex:0 0 auto}h1,h2,h3,h4,h5,h6{font-family:Poppins,sans-serif;margin-top:0;font-weight:600}header{background:#ffffffd9;-webkit-backdrop-filter:blur(10px);backdrop-filter:blur(10px);box-shadow:var(--shadow-sm);border-bottom:1px solid var(--border-primary);position:sticky;top:0;z-index:100;padding:var(--spacing-sm) var(--spacing-lg);display:flex;justify-content:space-between;align-items:center;gap:var(--spacing-sm)}.logo{display:flex;align-items:center;gap:var(--spacing-sm);min-width:0;flex:1 1 auto}.logo h1{margin:0;font-size:1.5rem;font-weight:700;color:var(--text-primary);line-height:1;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}.logo .logo-icon{width:28px;height:28px;flex:0 0 28px;display:block;filter:drop-shadow(0 -.5mm .75mm #0b5ea8);position:relative;top:-2px}nav ul{display:none}.premium-pill:after{content:"Premium";margin-left:8px;font-size:.7rem;color:var(--text-accent);background:#2563eb1a;border:1px solid rgba(37,99,235,.3);padding:2px 6px;border-radius:999px}#premium-modal .modal-content{max-width:520px;padding:var(--spacing-xl)}#premium-modal ul{margin:var(--spacing-md) 0;padding-left:1.2rem}.premium-actions{display:flex;gap:var(--spacing-sm);margin-top:var(--spacing-md)}.page-title{text-align:center;margin-bottom:var(--spacing-xl)}.page-title h2{font-size:2.25rem;font-weight:700;color:var(--text-primary);margin-bottom:var(--spacing-sm)}.page-title p{color:var(--text-secondary);font-size:1.1rem;max-width:600px;margin:0 auto}.level-selector-container{margin-bottom:var(--spacing-xl);display:flex;justify-content:center;width:100%;padding:4px 8px;box-sizing:border-box}.level-selector{margin-bottom:var(--spacing-xl);display:flex;justify-content:center;gap:var(--spacing-sm);flex-wrap:nowrap;white-space:nowrap;align-items:center}.level-selector button{background:var(--bg-secondary);border:1px solid var(--border-primary);color:var(--text-secondary);font-weight:500;padding:8px 12px;border-radius:var(--border-radius-sm);cursor:pointer;transition:var(--transition);font-size:clamp(12px,1.6vw,14px);box-shadow:var(--shadow-sm);flex:0 0 auto}.level-selector button:hover{background:var(--bg-hover);color:var(--text-primary);border-color:var(--border-secondary)}.level-selector button.active{background:var(--text-accent);color:#fff;border-color:var(--text-accent);font-weight:600}#level-selector{list-style:none;padding:var(--spacing-xs);display:flex;justify-content:center;gap:var(--spacing-sm);margin:0;background:var(--bg-secondary);border-radius:var(--border-radius);box-shadow:var(--shadow-sm);border:1px solid var(--border-primary);overflow:visible}#level-selector button{background:transparent;border:none;color:var(--text-secondary);font-weight:500;padding:8px 12px;border-radius:var(--border-radius-sm);cursor:pointer;transition:var(--transition);font-size:clamp(12px,1.6vw,14px);white-space:nowrap;flex:0 0 auto}#level-selector button:hover{background:var(--bg-hover);color:var(--text-primary)}#level-selector button.active{background:var(--bg-tertiary);color:var(--text-accent);font-weight:600;box-shadow:inset 0 2px 4px #00000008}@media (max-width: 480px){.level-selector{gap:6px}.level-selector button,#level-selector button{padding:6px 8px;font-size:clamp(11px,3.8vw,13px)}.level-selector-container{padding:2px 6px}}@media (max-width: 340px){.level-selector-container{overflow-x:auto;-webkit-overflow-scrolling:touch}.level-selector{justify-content:flex-start;padding-left:6px}.level-selector-container::-webkit-scrollbar{height:8px}.level-selector-container::-webkit-scrollbar-thumb{background:#00000014;border-radius:999px}}#search-container{margin-bottom:var(--spacing-xl)}#search-form{max-width:700px;margin:0 auto}.search-input-container{position:relative;display:flex;align-items:center}#search-input{width:100%;padding:var(--spacing-md) var(--spacing-lg);border:1px solid var(--border-primary);background:var(--bg-secondary);border-radius:var(--border-radius);font-size:1rem;color:var(--text-primary);font-weight:500;transition:var(--transition);box-shadow:var(--shadow-sm)}#search-input:focus{outline:none;border-color:var(--border-focus);box-shadow:0 0 0 3px #2563eb1a}#search-input::placeholder{color:var(--text-muted);font-weight:400}.search-clear-btn{position:absolute;right:var(--spacing-md);background:none;border:none;color:var(--text-muted);cursor:pointer;padding:var(--spacing-xs);font-size:1.2rem;transition:var(--transition)}.search-icon{position:absolute;left:var(--spacing-md);color:var(--text-muted);pointer-events:none}#search-input{padding-left:44px}.search-clear-btn:hover{color:var(--text-primary)}.search-clear-btn.hidden{display:none}.controls{display:flex;gap:var(--spacing-md);align-items:center;flex:0 0 auto}.controls select{padding:var(--spacing-sm) var(--spacing-md);border:1px solid var(--border-primary);border-radius:var(--border-radius-sm);background:var(--bg-secondary);color:var(--text-secondary);cursor:pointer;transition:var(--transition);font-weight:500;font-size:.9rem;box-shadow:var(--shadow-sm)}.controls select:hover{border-color:var(--border-secondary)}.controls select:focus{outline:none;border-color:var(--border-focus);box-shadow:0 0 0 3px #2563eb1a}#vocabulary-container{display:flex;flex-direction:column;gap:var(--spacing-md);margin-bottom:var(--spacing-lg)}.word-item{background:var(--bg-secondary);border-radius:var(--border-radius);padding:var(--spacing-md) var(--spacing-lg);box-shadow:var(--shadow-sm);transition:var(--transition);border:1px solid var(--border-primary);display:flex;align-items:center;justify-content:space-between;position:relative;overflow:visible;z-index:1}.word-item.word-item-active{z-index:100}.word-item:before{content:"";position:absolute;left:0;top:0;bottom:0;width:4px;background-color:var(--bg-tertiary);transition:var(--transition)}.word-item:hover{box-shadow:var(--shadow-md);transform:translateY(-2px);border-color:var(--border-secondary)}.word-item:hover:before{background-color:var(--text-accent)}.word-info{flex-grow:1;padding-right:var(--spacing-lg)}.word-info h3{margin:0 0 var(--spacing-xs) 0;color:var(--text-primary);font-size:1.2rem;font-weight:600}.word-info .translation{color:var(--text-secondary);font-size:1rem;font-weight:500}.word-info .example{font-style:italic;color:var(--text-muted);font-size:.9rem;margin-top:var(--spacing-sm);border-left:3px solid var(--border-primary);padding-left:var(--spacing-md)}.play-button{background:var(--bg-tertiary);color:var(--text-accent);border:none;width:44px;height:44px;border-radius:50%;display:flex;align-items:center;justify-content:center;cursor:pointer;transition:var(--transition);flex-shrink:0;font-size:1.2rem}.play-button:hover{background:#dbeafe;transform:scale(1.1)}.play-button:active{transform:scale(.95)}.search-results-header{padding:var(--spacing-lg);border-radius:var(--border-radius-lg);margin-bottom:var(--spacing-lg);text-align:center;background:var(--bg-tertiary)}.search-results-header h3{color:var(--text-primary);margin:0;font-size:1.2rem;font-weight:600}.level-group{margin-bottom:var(--spacing-xl)}.level-header{background:var(--bg-tertiary);color:var(--text-primary);padding:var(--spacing-md) var(--spacing-lg);border-radius:var(--border-radius);display:flex;justify-content:space-between;align-items:center;cursor:pointer;transition:var(--transition);font-weight:600;box-shadow:var(--shadow-sm);border:1px solid var(--border-secondary);margin-bottom:var(--spacing-sm)}.level-header:hover{background:var(--bg-hover)}.level-header span{font-size:1.1rem}.collapse-btn{background:none;border:none;color:var(--text-secondary);font-size:1.5rem;cursor:pointer;transition:var(--transition)}.level-words-container{display:flex;flex-direction:column;gap:var(--spacing-md)}.navigation{display:flex;justify-content:center;align-items:center;gap:var(--spacing-md);margin:var(--spacing-xl) 0}.navigation button{background:var(--bg-secondary);color:var(--text-primary);border:1px solid var(--border-primary);padding:var(--spacing-sm) var(--spacing-lg);border-radius:var(--border-radius-sm);cursor:pointer;transition:var(--transition);font-weight:500;font-size:.9rem;box-shadow:var(--shadow-sm)}.navigation button:hover:not(:disabled){background:var(--bg-hover);border-color:var(--border-secondary)}.navigation button:first-of-type,.navigation button:last-of-type{background:var(--text-accent);color:#fff;border-color:var(--text-accent);font-weight:600}.navigation button:first-of-type:hover:not(:disabled),.navigation button:last-of-type:hover:not(:disabled){background:#1d4ed8;border-color:#1d4ed8}.navigation button:disabled{background:var(--bg-primary);color:var(--text-muted);cursor:not-allowed;opacity:.7}#page-info{font-weight:500;color:var(--text-secondary);font-size:1rem;padding:var(--spacing-sm) var(--spacing-md)}#scroll,#scroll2{position:fixed;right:24px;background:var(--bg-secondary);color:var(--text-secondary);border:1px solid var(--border-primary);border-radius:50%;width:48px;height:48px;display:flex;align-items:center;justify-content:center;cursor:pointer;transition:var(--transition);box-shadow:var(--shadow-md);z-index:1001;font-size:1.2rem;opacity:0;visibility:hidden;transform:translateY(20px);transition:opacity .3s,transform .3s,visibility .3s}#scroll.show-scroll,#scroll2.show-scroll{opacity:1;visibility:visible;transform:translateY(0)}#scroll{bottom:80px}#scroll2{bottom:24px}#scroll:hover,#scroll2:hover{background:var(--bg-hover);color:var(--text-primary);transform:scale(1.1)}.hidden{display:none!important}.ad-item{border:1px dashed var(--border-secondary)!important;background:repeating-linear-gradient(-45deg,var(--bg-primary),var(--bg-primary) 10px,#fcfcfd 10px,#fcfcfd 20px)!important;box-shadow:none!important;transform:none!important}.ad-content{width:100%;text-align:center;color:var(--text-muted);font-size:.9rem}.ad-label{font-size:.75rem;font-weight:600;text-transform:uppercase;letter-spacing:.05em;color:var(--text-muted);margin-bottom:var(--spacing-sm)}footer{background:var(--bg-secondary);border-top:1px solid var(--border-primary);text-align:center;padding:var(--spacing-lg);margin-top:var(--spacing-2xl);color:var(--text-muted)}footer a{color:var(--text-secondary);text-decoration:none;font-weight:500;transition:var(--transition)}footer a:hover{color:var(--text-accent);text-decoration:underline}.page-title h2{background:linear-gradient(120deg,var(--text-primary),var(--text-accent));-webkit-background-clip:text;-webkit-text-fill-color:transparent;background-clip:text;padding-bottom:var(--spacing-xs)}.quiz-section,.video-section{background:var(--bg-secondary);padding:var(--spacing-xl);border-radius:var(--border-radius-lg);box-shadow:var(--shadow-md);border:1px solid var(--border-primary)}.quiz-config-container{max-width:600px;margin:0 auto;display:flex;flex-direction:column;gap:var(--spacing-lg)}.form-group{display:flex;flex-direction:column;gap:var(--spacing-sm)}.form-group label{font-weight:600;color:var(--text-primary)}.form-group select,.filter-group select,.filter-group input{width:100%;padding:var(--spacing-md);border:1px solid var(--border-primary);border-radius:var(--border-radius-sm);background:var(--bg-primary);color:var(--text-primary);font-weight:500;transition:var(--transition);box-shadow:var(--shadow-sm)}.form-group select:focus,.filter-group select:focus,.filter-group input:focus{outline:none;border-color:var(--border-focus);box-shadow:0 0 0 3px #2563eb1a}.radio-group{display:flex;flex-wrap:wrap;gap:var(--spacing-md);background:var(--bg-primary);padding:var(--spacing-sm);border-radius:var(--border-radius-sm)}.radio-group input[type=radio]{display:none}.radio-group label{font-weight:500;cursor:pointer;padding:var(--spacing-sm) var(--spacing-md);border-radius:var(--border-radius-sm);transition:var(--transition);border:1px solid transparent}.radio-group input[type=radio]:checked+label{background:var(--bg-secondary);color:var(--text-accent);font-weight:600;border-color:var(--border-secondary);box-shadow:var(--shadow-sm)}.btn-primary{background:var(--text-accent);color:#fff;border:none;padding:var(--spacing-md);font-size:1.1rem;font-weight:600;border-radius:var(--border-radius-sm);cursor:pointer;transition:var(--transition);box-shadow:var(--shadow-md)}.btn-primary:hover{background:#1d4ed8}.video-filters{display:flex;gap:var(--spacing-lg);margin-bottom:var(--spacing-xl);align-items:center}.filter-group{flex-grow:1}.video-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:var(--spacing-lg)}.video-card{background:var(--bg-secondary);border-radius:var(--border-radius);box-shadow:var(--shadow-sm);border:1px solid var(--border-primary);overflow:hidden;transition:var(--transition);cursor:pointer}.video-card:hover{transform:translateY(-4px);box-shadow:var(--shadow-lg)}.video-thumbnail img{width:100%;display:block}.video-thumbnail .play-icon{position:absolute;top:50%;left:50%;transform:translate(-50%,-50%);width:60px;height:60px;background:#0009;border-radius:50%;display:flex;align-items:center;justify-content:center;color:#fff;font-size:2rem;transition:var(--transition)}.video-card:hover .play-icon{transform:translate(-50%,-50%) scale(1.1);background:var(--text-accent)}.video-info{padding:var(--spacing-md)}.video-info h4{margin:0 0 var(--spacing-sm) 0;font-size:1.1rem}.video-info p{margin:0;color:var(--text-secondary);font-size:.9rem}.modal{position:fixed;z-index:200;left:0;top:0;width:100%;height:100%;background:#000000b3;display:none;align-items:center;justify-content:center;-webkit-backdrop-filter:blur(5px);backdrop-filter:blur(5px)}.modal.show{display:flex}.modal-content{position:relative;width:90%;max-width:600px;background:var(--bg-secondary);border-radius:var(--border-radius-lg);box-shadow:var(--shadow-lg)}.modal-content .close-btn{position:absolute;top:-40px;right:0;color:#fff;font-size:2.5rem;font-weight:700;cursor:pointer}#youtube-player{aspect-ratio:16 / 9;width:100%}#youtube-player iframe{width:100%;height:100%;border:none;border-radius:var(--border-radius-lg)}#inline-video-player{aspect-ratio:16 / 9;width:100%;background:#000;border-radius:var(--border-radius-lg);overflow:hidden;box-shadow:var(--shadow-md);margin-bottom:var(--spacing-xl)}#inline-video-player iframe{width:100%;height:100%;border:0}.quiz-header{margin-bottom:var(--spacing-xl);padding:var(--spacing-lg);background:var(--bg-secondary);border-radius:var(--border-radius-lg);box-shadow:var(--shadow-sm);border:1px solid var(--border-primary)}.progress-text{font-weight:600;color:var(--text-primary);margin-bottom:var(--spacing-sm)}.progress-bar{width:100%;height:8px;background-color:var(--bg-tertiary);border-radius:4px;overflow:hidden}.progress-fill{height:100%;background-color:var(--text-accent);transition:width .3s ease-in-out;border-radius:4px}.quiz-question h3{font-size:1.5rem;margin-bottom:var(--spacing-lg);color:var(--text-primary);text-align:center}.options-list{list-style:none;padding:0;display:grid;grid-template-columns:repeat(2,1fr);gap:var(--spacing-md)}.option-button{width:100%;padding:var(--spacing-lg);background:var(--bg-secondary);border:1px solid var(--border-primary);border-radius:var(--border-radius);cursor:pointer;transition:var(--transition);text-align:left;font-size:1rem;font-weight:500;color:var(--text-primary);box-shadow:var(--shadow-sm)}.option-button:hover:not(:disabled){background:var(--bg-hover);border-color:var(--border-focus);transform:translateY(-2px)}.option-button.selected{border-color:var(--border-focus);background-color:var(--bg-tertiary);color:var(--text-primary)}.option-button.correct{background:#dcfce7;color:#166534;border-color:#16a34a;font-weight:600}.option-button.incorrect{background:#fee2e2;color:#991b1b;border-color:#ef4444;font-weight:600}.option-button:disabled{cursor:not-allowed;opacity:.8}.feedback-container{margin-top:var(--spacing-lg);min-height:50px}.feedback{padding:var(--spacing-md);border-radius:var(--border-radius);display:flex;align-items:center;gap:var(--spacing-md);font-weight:600}.feedback.correct{background-color:#dcfce7;color:#166534}.feedback.incorrect{background-color:#fee2e2;color:#991b1b}.feedback .icon{font-size:1.5rem}.quiz-navigation{margin-top:var(--spacing-xl);display:flex;justify-content:space-between;gap:var(--spacing-md)}.quiz-results{text-align:center;background:var(--bg-secondary);padding:var(--spacing-2xl);border-radius:var(--border-radius-lg);box-shadow:var(--shadow-lg)}.quiz-results h3{font-size:2.5rem;color:var(--text-primary);margin-bottom:var(--spacing-md)}.quiz-score{font-size:4rem;font-weight:700;color:var(--text-accent);margin:var(--spacing-md) 0}.quiz-percentage,.quiz-time{font-size:1.2rem;color:var(--text-secondary);margin-bottom:var(--spacing-2xl)}.quiz-summary{text-align:left;margin-top:var(--spacing-xl)}.quiz-summary h4{font-size:1.2rem;color:var(--text-primary);margin-bottom:var(--spacing-lg);border-bottom:1px solid var(--border-primary);padding-bottom:var(--spacing-sm)}.results-list{list-style:none;padding:0;display:flex;flex-direction:column;gap:var(--spacing-sm)}.results-list li{padding:var(--spacing-md);border-radius:var(--border-radius);border-left:4px solid}.results-list li.correct{background-color:#f0fdf4;border-left-color:#22c55e}.results-list li.incorrect{background-color:#fef2f2;border-left-color:#ef4444}.question-number{font-weight:600;margin-right:var(--spacing-sm)}.answer-info{margin-top:var(--spacing-sm);font-size:.9rem;color:var(--text-muted)}.correct-answer{color:#15803d;font-weight:600}.quiz-actions{margin-top:var(--spacing-xl);display:flex;justify-content:center;gap:var(--spacing-md)}.video-item{background:var(--bg-secondary);border-radius:var(--border-radius);box-shadow:var(--shadow-sm);border:1px solid var(--border-primary);overflow:hidden;transition:var(--transition);cursor:pointer;display:flex;flex-direction:column}.video-item:hover{transform:translateY(-4px);box-shadow:var(--shadow-lg)}.video-item .category-badge{position:absolute;top:var(--spacing-md);right:var(--spacing-md);background:#00000080;color:#fff;padding:var(--spacing-xs) var(--spacing-sm);border-radius:var(--border-radius-sm);font-size:.8rem;font-weight:600;text-transform:capitalize}.video-item img{width:100%;display:block;aspect-ratio:16/9;object-fit:cover}.video-item .play-overlay{position:absolute;top:0;left:0;right:0;bottom:0;background:#0003;display:flex;align-items:center;justify-content:center;opacity:0;transition:var(--transition)}.video-item:hover .play-overlay{opacity:1}.video-item .play-icon{color:#fff;font-size:3rem}.video-item .title{font-weight:600;padding:var(--spacing-md) var(--spacing-md) var(--spacing-xs)}.video-item .description{font-size:.9rem;color:var(--text-secondary);padding:0 var(--spacing-md) var(--spacing-md);flex-grow:1}.no-videos{text-align:center;color:var(--text-muted);font-style:italic;padding:var(--spacing-2xl);background:var(--bg-secondary);border-radius:var(--border-radius-lg)}@media (max-width: 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.sidebar-inner{position:static;top:0;height:100%;display:flex;flex-direction:column}.sidebar-header{display:flex}.sidebar-nav{flex:1;overflow-y:auto}main{max-width:100%;padding-left:0}header{margin-bottom:var(--spacing-lg)}.sidebar-toggle{display:inline-flex;min-width:48px}}@media (min-width: 901px){.app-container{display:grid;grid-template-columns:260px 1fr}.sidebar{position:fixed;left:0;top:72px;height:calc(100vh - 72px);width:260px;z-index:1001}main{grid-column:2 / -1;max-width:none;margin:0}}@media (max-width: 768px){body{font-size:15px}main{padding:var(--spacing-md)}header{padding:6px var(--spacing-md);min-height:52px;position:sticky;top:0;background:#ffffffd9;-webkit-backdrop-filter:blur(10px);backdrop-filter:blur(10px);z-index:100}.logo h1{font-size:1.1rem}.logo .logo-icon{width:22px;height:22px;flex-basis:22px}header .btn-secondary{padding:6px 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p{font-size:1rem}#level-selector{flex-wrap:wrap;padding:var(--spacing-sm)}.word-item{flex-direction:column;align-items:flex-start;gap:var(--spacing-sm)}.word-info{width:100%}.play-button{align-self:flex-end}.options-list{grid-template-columns:1fr}.quiz-navigation,.quiz-actions{flex-direction:column}.quiz-results{padding:var(--spacing-lg)}.quiz-score{font-size:3rem}.video-filters{flex-direction:column;align-items:stretch}.video-grid{grid-template-columns:1fr}#scroll,#scroll2{width:48px;height:48px;right:16px}#scroll{bottom:80px}#scroll2{bottom:24px}.btn-primary,.btn-secondary,button{min-height:44px;min-width:44px;padding:var(--spacing-sm) var(--spacing-md)}.sidebar-nav a{min-height:48px;padding:var(--spacing-md);font-size:1rem}.word-item{padding:var(--spacing-md);margin-bottom:var(--spacing-sm)}.modal-content{margin:var(--spacing-sm);max-height:calc(100vh - 2 * var(--spacing-sm));overflow-y:auto}p,li{line-height:1.7}a{color:var(--text-accent);text-decoration:underline}a:hover,a:focus{color:var(--text-primary);text-decoration:none}}.video-thumbnail{position:relative}.control-group{display:flex;align-items:center;gap:var(--spacing-sm)}.control-group label{font-size:.9rem;font-weight:500;color:var(--text-secondary)}.navigation-tip{text-align:center;color:var(--text-muted);font-size:.9rem;margin-top:var(--spacing-md);display:flex;align-items:center;justify-content:center;gap:var(--spacing-sm)}.tip-icon{width:16px;height:16px}.save-icon-container{position:absolute;top:8px;right:8px}.save-icon{color:var(--text-muted);transition:all .2s ease-in-out;font-size:1.2rem}.save-icon.saved{color:var(--text-accent);fill:var(--text-accent)}.save-icon:hover{color:var(--text-accent);transform:scale(1.1)}.lists-popup{display:none;position:absolute;top:100%;right:0;background-color:var(--bg-secondary);border:1px solid var(--border-primary);border-radius:var(--border-radius);box-shadow:var(--shadow-lg);z-index:9999;width:220px;padding:var(--spacing-md);max-height:300px;overflow-y:auto;opacity:0;transform:translateY(-10px);transition:all .2s ease-in-out}.lists-popup.show{opacity:1;transform:translateY(0)}.lists-popup ul{list-style:none;padding:0;margin:0}.lists-popup li{padding:var(--spacing-sm) var(--spacing-md);cursor:pointer;border-radius:var(--border-radius-sm);margin-bottom:2px;transition:all .1s ease-in-out;display:flex;align-items:center;justify-content:space-between}.lists-popup li:hover{background-color:var(--bg-hover);transform:translate(2px)}.lists-popup li.saved{background-color:#2563eb1a;color:var(--text-accent);font-weight:500}.lists-popup li.saved:after{content:"✓";color:var(--text-accent);font-weight:700}.lists-popup input[type=text]{width:100%;padding:var(--spacing-sm);margin-top:var(--spacing-sm);border:1px solid var(--border-primary);border-radius:var(--border-radius-sm);font-size:.9rem;transition:border-color .2s ease-in-out}.lists-popup input[type=text]:focus{outline:none;border-color:var(--text-accent);box-shadow:0 0 0 2px #2563eb1a}.lists-popup h4{margin:0 0 var(--spacing-sm) 0;font-size:.9rem;color:var(--text-secondary);text-transform:uppercase;letter-spacing:.5px}.premium-upsell{background:var(--bg-tertiary);border:1px dashed var(--border-secondary);color:var(--text-secondary);padding:var(--spacing-sm) var(--spacing-md);border-radius:var(--border-radius-sm)}.premium-upsell a{color:var(--text-accent);font-weight:600;text-decoration:none}.premium-upsell a:hover{text-decoration:underline}.lists-popup input[disabled],.lists-popup input[aria-disabled=true],.lists-popup input[data-locked=true]{background:var(--bg-primary);color:var(--text-muted);border-style:dashed;cursor:not-allowed}#level-selector button.premium-locked{position:relative;opacity:.7;cursor:pointer}#level-selector button.premium-locked:after{content:"🔒";margin-left:6px;font-size:.85rem;color:var(--text-accent)}#premium-button.btn-primary{background:linear-gradient(180deg,#2a6af0,#1d4ed8);box-shadow:0 6px 18px #2563eb59,inset 0 1px #ffffff26}#premium-button.btn-primary:hover{background:linear-gradient(180deg,#2960da,#1b46c2)}#flashcard-view{position:fixed;top:0;left:0;width:100%;height:100%;background:var(--bg-primary);z-index:1000;display:none;flex-direction:column;align-items:center;justify-content:center;padding:var(--spacing-lg);box-sizing:border-box;gap:var(--spacing-lg)}#flashcard-container{perspective:1000px;width:100%;flex-grow:1;display:flex;align-items:center;justify-content:center}.flashcard{width:100%;max-width:500px;height:60%;max-height:400px;perspective:1000px;background-color:transparent;cursor:pointer}.flashcard:focus{outline:none}.flashcard:focus-visible .flashcard-inner{box-shadow:0 0 0 3px var(--border-focus);border-radius:var(--border-radius-lg)}.flashcard-inner{position:relative;width:100%;height:100%;transition:transform .6s;transform-style:preserve-3d}.flashcard.flipped .flashcard-inner{transform:rotateY(180deg)}.flashcard-front,.flashcard-back{position:absolute;width:100%;height:100%;backface-visibility:hidden;display:flex;align-items:center;justify-content:center;font-size:clamp(1.5rem,5vw,2.5rem);font-weight:600;background:var(--bg-secondary);border-radius:var(--border-radius-lg);box-shadow:var(--shadow-lg);border:1px solid var(--border-primary);padding:var(--spacing-lg);text-align:center;box-sizing:border-box;overflow-wrap:break-word;word-break:break-word}.flashcard-back{transform:rotateY(180deg);font-size:clamp(1.2rem,4vw,2rem);font-weight:500}.flashcard-navigation{display:none}.anki-buttons{display:grid;grid-template-columns:1fr 1fr;gap:var(--spacing-md);width:100%;max-width:500px;margin-top:0;box-sizing:border-box}.anki-buttons button{padding:var(--spacing-lg);font-size:1.1rem;height:auto}.anki-buttons button:disabled,.btn-anki:disabled{opacity:.6;cursor:not-allowed;filter:grayscale(20%)}.study-header{width:100%;max-width:800px;display:grid;grid-template-columns:120px 1fr auto;align-items:center;gap:var(--spacing-md)}.study-progress{text-align:center;color:var(--text-secondary)}.study-help{color:var(--text-muted);font-size:.9rem}.study-stats{width:100%;max-width:800px;display:flex;gap:var(--spacing-sm);flex-wrap:wrap}.stat-pill{display:inline-flex;align-items:center;gap:8px;padding:6px 10px;border-radius:999px;background:var(--bg-secondary);border:1px solid var(--border-primary);color:var(--text-secondary);font-size:.9rem}.stat-pill strong{color:var(--text-primary)}.stat-pill.again{border-color:#ef44444d}.stat-pill.hard{border-color:#f59e0b4d}.stat-pill.good{border-color:#22c55e4d}.stat-pill.easy{border-color:#3b82f64d}.btn-anki{position:relative}.btn-anki 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rgba(59,130,246,.3)}.btn-anki-again:hover{background:#ef444426}.btn-anki-hard:hover{background:#f59e0b26}.btn-anki-good:hover{background:#22c55e26}.btn-anki-easy:hover{background:#3b82f626}.study-complete{text-align:center;margin-top:var(--spacing-xl)}#study-view .study-options{background:transparent;padding:0;border-radius:0;box-shadow:none;border:none;display:grid;grid-template-columns:minmax(0,1fr) 320px;gap:var(--spacing-xl);align-items:start}#study-view #scope-selection-container{background:var(--bg-secondary);border:1px solid var(--border-primary);border-radius:var(--border-radius-lg);padding:var(--spacing-lg);max-height:70vh;overflow-y:auto}#study-view .scope-level,#study-view .scope-chapter,#study-view .scope-group{margin-bottom:var(--spacing-sm)}#study-view .scope-chapter{margin-left:var(--spacing-md);padding-left:var(--spacing-md);border-left:2px solid var(--bg-tertiary)}#study-view .scope-group{margin-left:var(--spacing-md)}#study-view .scope-item-header{display:flex;align-items:center;gap:var(--spacing-md);padding:var(--spacing-sm) var(--spacing-md);border-radius:var(--border-radius-sm);cursor:pointer;transition:var(--transition);border:1px solid transparent}#study-view .scope-item-header:hover{background:var(--bg-hover);border-color:var(--border-secondary)}#study-view .scope-toggle-icon{color:var(--text-muted);transition:transform .2s ease}#study-view .scope-item-header.collapsed .scope-toggle-icon{transform:rotate(0)}#study-view .scope-item-header:not(.collapsed) .scope-toggle-icon{transform:rotate(90deg)}#study-view .study-settings{position:sticky;top:84px;align-self:start;background:var(--bg-secondary);border:1px solid var(--border-primary);border-radius:var(--border-radius-lg);padding:var(--spacing-lg);display:flex;flex-direction:column;gap:var(--spacing-xl)}#study-view .study-settings .study-actions{display:flex;gap:var(--spacing-sm)}#study-view .sticky-actions{padding-top:var(--spacing-md);display:flex;justify-content:flex-end}@media (max-width: 900px){#study-view .study-options{grid-template-columns:1fr}#study-view .study-settings{position:static;top:auto}#study-view .sticky-actions{justify-content:stretch}#study-view .sticky-actions .btn-primary{width:100%}}.breadcrumb{display:flex;gap:8px;align-items:center;color:var(--text-secondary);margin-bottom:var(--spacing-md)}.breadcrumb a{color:var(--text-accent);text-decoration:none}.breadcrumb a:hover{text-decoration:underline}#study-view .quiz-actions{grid-column:1 / -1}@media (max-width: 900px){#study-view .study-options{grid-template-columns:1fr}}.final-stats{margin:var(--spacing-md) 0 var(--spacing-lg);color:var(--text-secondary)}.study-options{padding:var(--spacing-lg);display:flex;flex-direction:column;gap:var(--spacing-lg)}#scope-selection-container{display:flex;flex-direction:column;gap:var(--spacing-sm)}.scope-level{padding:0;border:none;border-radius:0}.scope-level-header{display:flex;align-items:center;gap:var(--spacing-sm);cursor:pointer;font-weight:600;font-size:1.1rem;padding:var(--spacing-sm);border-radius:var(--border-radius-sm);transition:var(--transition)}.scope-level-header:hover{background:var(--bg-hover)}.scope-level-header input[type=checkbox]{margin-right:var(--spacing-sm)}.chapter-list,.group-list{padding-left:var(--spacing-lg);display:none}.chapter-item,.group-item{display:flex;align-items:center;gap:var(--spacing-sm);margin-top:var(--spacing-sm)}.sidebar-footer{padding:var(--spacing-md);border-top:1px solid var(--border-primary);margin-top:auto}.user-profile-container{display:flex;flex-direction:column;gap:var(--spacing-md)}#user-info{display:flex;flex-direction:column;align-items:flex-start;gap:var(--spacing-sm)}#user-email{font-weight:500;color:var(--text-secondary);font-size:.9rem}#auth-buttons,#user-info>button{width:100%}.btn-secondary{background:var(--bg-tertiary);color:var(--text-primary);border:1px solid var(--border-primary);padding:var(--spacing-sm) var(--spacing-md);border-radius:var(--border-radius-sm);cursor:pointer;transition:var(--transition);font-weight:500}.btn-secondary:hover{background:var(--bg-hover);border-color:var(--border-secondary)}#auth-modal .modal-content{max-width:400px;padding:var(--spacing-xl)}#auth-modal h2{text-align:center;margin-bottom:var(--spacing-lg)}#auth-modal form{display:flex;flex-direction:column;gap:var(--spacing-md)}#auth-modal input{padding:var(--spacing-md);border:1px solid var(--border-primary);border-radius:var(--border-radius-sm);font-size:1rem}#auth-modal button{padding:var(--spacing-md)}#auth-modal .form-footer{text-align:center;margin-top:var(--spacing-md);font-size:.9rem;color:var(--text-secondary)}#auth-modal .form-footer a{color:var(--text-accent);cursor:pointer;font-weight:500}#notification-container{position:fixed;top:80px;right:20px;z-index:1000;display:flex;flex-direction:column;gap:var(--spacing-md)}.notification{background-color:var(--bg-secondary);color:var(--text-primary);padding:var(--spacing-md) var(--spacing-lg);border-radius:var(--border-radius-sm);box-shadow:var(--shadow-lg);border-left:4px solid;opacity:0;transform:translate(100%);transition:all .5s ease-in-out}.notification.show{opacity:1;transform:translate(0)}.notification.success{border-left-color:var(--success)}.notification.error{border-left-color:var(--error)}#study-modal .modal-content{width:90%;max-width:600px;max-height:80vh;display:flex;flex-direction:column}#scope-selection-container{overflow-y:auto;flex-grow:1;padding-right:1rem}.scope-level,.scope-chapter,.scope-group{margin-left:1rem}.scope-item-header{cursor:pointer;padding:.25rem;display:flex;align-items:center}.scope-item-header:hover{background-color:#f0f0f0}.scope-chapters-container,.scope-groups-container{display:none;margin-left:0;border-left:none;padding-left:0;margin-top:var(--spacing-sm)}#lists-container{display:grid;grid-template-columns:repeat(auto-fill,minmax(300px,1fr));gap:var(--spacing-lg);margin-bottom:var(--spacing-xl)}.list-card{background:var(--bg-secondary);border-radius:var(--border-radius);padding:var(--spacing-lg);box-shadow:var(--shadow-sm);border:1px solid var(--border-primary);cursor:pointer;transition:var(--transition)}.list-card:hover{box-shadow:var(--shadow-md);transform:translateY(-2px);border-color:var(--border-secondary)}.list-card h3{margin:0 0 var(--spacing-sm) 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