.learn-header{padding:20px 0 12px;border-bottom:1px solid var(--border);margin-bottom:0}.learn-header-top{display:flex;align-items:center;justify-content:space-between;margin-bottom:12px}.learn-header h1{font-size:1.5rem;font-weight:700;margin:0}.audience-toggle{display:flex;background:var(--bg);border:1px solid var(--border);border-radius:8px;overflow:hidden}.aud-btn{background:none;border:none;padding:6px 16px;font-size:13px;font-weight:600;color:var(--muted);cursor:pointer;transition:all .15s}.aud-btn.active{background:var(--accent);color:#fff}.learn-filters{display:flex;gap:16px;align-items:center}.filter-group{display:flex;align-items:center;gap:6px}.filter-group label{font-size:12px;color:var(--muted);font-weight:600}.filter-group select{width:auto;min-width:120px;padding:4px 8px;font-size:13px}.cat-tabs{display:flex;gap:2px;border-bottom:2px solid var(--border);margin-bottom:0;overflow-x:auto;-webkit-overflow-scrolling:touch}.cat-tab{background:none;border:none;padding:10px 14px;color:var(--muted);cursor:pointer;font-size:13px;font-weight:600;border-bottom:2px solid transparent;margin-bottom:-2px;transition:color .15s,border-color .15s;white-space:nowrap}.cat-tab:hover{color:var(--text)}.cat-tab.active{color:var(--accent);border-bottom-color:var(--accent)}.learn-layout{display:grid;grid-template-columns:280px 1fr;gap:0;min-height:calc(100vh - 200px)}.learn-sidebar{border-right:1px solid var(--border);overflow-y:auto;max-height:calc(100vh - 200px);position:sticky;top:52px;padding:12px 0}.sidebar-progress{padding:8px 12px 12px}.progress-text{font-size:11px;color:var(--muted);margin-bottom:4px}.progress-bar{height:4px;background:var(--border);border-radius:2px;overflow:hidden}.progress-fill{height:100%;background:var(--green);border-radius:2px;transition:width .3s}.lesson-group-label{font-size:10px;font-weight:700;text-transform:uppercase;letter-spacing:.08em;color:var(--muted);padding:12px 12px 4px}.lesson-item{display:flex;align-items:center;gap:8px;padding:8px 12px;cursor:pointer;border-left:3px solid transparent;transition:background .15s,border-color .15s}.lesson-item:hover{background:var(--surface2)}.lesson-item.active{background:var(--surface2);border-left-color:var(--accent)}.lesson-item.completed .lesson-item-title{color:var(--muted)}.lesson-icon{font-size:18px;flex-shrink:0;width:24px;text-align:center}.lesson-item-body{flex:1;min-width:0}.lesson-item-title{font-size:13px;font-weight:600;color:var(--text);white-space:nowrap;overflow:hidden;text-overflow:ellipsis}.lesson-item-meta{font-size:11px;color:var(--muted);margin-top:1px}.lesson-check{color:var(--green);font-weight:700;font-size:14px;flex-shrink:0}.learn-viewer{padding:24px 32px;overflow-y:auto;max-height:calc(100vh - 200px)}.viewer-empty{text-align:center;padding:80px 20px;color:var(--muted)}.viewer-empty-icon{font-size:48px;margin-bottom:16px}.viewer-empty h2{font-size:1.25rem;margin-bottom:8px;color:var(--text)}.lesson-title-section{margin-bottom:24px;padding-bottom:16px;border-bottom:1px solid var(--border)}.lesson-title-section h2{font-size:1.4rem;font-weight:700;margin:0 0 4px}.lesson-subtitle{color:var(--muted);font-size:.95rem;margin:0 0 12px}.lesson-objectives{background:var(--surface);border:1px solid var(--border);border-radius:8px;padding:12px 16px;font-size:13px}.lesson-objectives strong{display:block;margin-bottom:6px;color:var(--accent);font-size:12px;text-transform:uppercase;letter-spacing:.05em}.lesson-objectives ul{margin:0;padding-left:18px}.lesson-objectives li{margin-bottom:3px;color:var(--text)}.lesson-text{font-size:14px;line-height:1.65;color:var(--text);margin:12px 0}.lesson-h3{font-size:1.1rem;font-weight:700;margin:24px 0 8px;color:var(--text)}.callout{border-radius:8px;padding:12px 16px;margin:14px 0;font-size:13px;line-height:1.55}.callout-label{display:block;font-weight:700;margin-bottom:4px;font-size:12px}.callout p{margin:0}.callout-tip{background:#f973161a;border:1px solid rgba(249,115,22,.25);color:#fb923c}.callout-warning{background:#ef44441a;border:1px solid rgba(239,68,68,.25);color:#f87171}.lesson-steps{margin:12px 0;padding-left:22px}.lesson-steps li{font-size:14px;line-height:1.6;margin-bottom:6px;color:var(--text)}.lesson-bullets{margin:12px 0;padding-left:20px}.lesson-bullets li{font-size:14px;line-height:1.6;margin-bottom:4px;color:var(--text)}.key-concept{background:var(--surface);border-left:3px solid var(--accent);padding:10px 14px;margin:14px 0;font-size:13px;line-height:1.55;border-radius:0 6px 6px 0;color:var(--text)}.diagram-wrap{margin:16px 0;background:var(--surface);border:1px solid var(--border);border-radius:10px;overflow:hidden}.diagram-svg{display:flex;justify-content:center;padding:12px;background:#fff;border-radius:8px 8px 0 0}.diagram-svg svg{max-width:100%;height:auto}.diagram-controls{padding:8px 12px;display:flex;gap:8px;justify-content:center}.quiz-section{margin-top:28px;padding-top:20px;border-top:1px solid var(--border)}.quiz-q{margin-bottom:16px}.quiz-question{font-size:14px;font-weight:600;margin-bottom:8px}.quiz-options{display:flex;flex-direction:column;gap:6px}.quiz-option{display:flex;align-items:center;gap:8px;font-size:13px;cursor:pointer;padding:6px 10px;border-radius:6px;transition:background .15s}.quiz-option:hover{background:var(--surface2)}.quiz-option input{width:auto;accent-color:var(--accent)}.quiz-result{font-size:13px;font-weight:600;margin-top:6px;min-height:20px}.quiz-correct{color:var(--green)}.quiz-wrong{color:var(--red)}.quiz-submit-btn{margin-top:8px}.lesson-bottom{margin-top:28px;padding-top:20px;border-top:1px solid var(--border);display:flex;gap:12px;align-items:center}.my-assignments-banner{background:var(--surface);border:1px solid var(--accent);border-radius:8px;padding:10px 14px;margin-bottom:12px}.my-assignments-header{display:flex;align-items:center;justify-content:space-between;margin-bottom:6px;font-size:13px}.my-assignments-list{display:flex;flex-wrap:wrap;gap:6px}.my-assignment-item{display:flex;align-items:center;gap:6px;padding:6px 10px;border-radius:6px;background:var(--bg);cursor:pointer;transition:background .15s;font-size:13px}.my-assignment-item:hover{background:var(--surface2)}.my-assignment-item.overdue{border-left:2px solid var(--red)}.my-assignment-body{flex:1}.my-assignment-title{font-weight:600;font-size:12px}.my-assignment-meta{font-size:10px;color:var(--muted)}@media (max-width: 768px){.learn-layout{grid-template-columns:1fr}.learn-sidebar{border-right:none;border-bottom:1px solid var(--border);max-height:none;position:static;padding:8px 0}.learn-viewer{padding:16px 12px;max-height:none}.learn-header-top{flex-direction:column;align-items:flex-start;gap:8px}.learn-filters{flex-wrap:wrap;gap:10px}.cat-tabs{gap:0}.cat-tab{padding:8px 10px;font-size:12px}.diagram-svg{padding:8px}}