*,*::before,*::after{box-sizing:border-box;margin:0;padding:0;}:root{--bg:#f4f5f8;--surface:#ffffff;--text:#14161d;--text-muted:#6b7280;--primary:#4f46e5;--primary-hover:#4338ca;--primary-soft:#eef2ff;--accent:#059669;--accent-bg:#ecfdf5;--warning:#d97706;--warning-bg:#fffbeb;--danger:#dc2626;--submitted:#7c3aed;--submitted-bg:#f3e8ff;--border:#e6e8ee;--radius:14px;--radius-sm:9px;--shadow:0 1px 3px rgba(20,22,29,0.06);--shadow-lg:0 10px 30px rgba(20,22,29,0.08);--content-max:1080px;}html{font-size:16px;}body{font-family:-apple-system,BlinkMacSystemFont,'Segoe UI',Roboto,sans-serif;background:var(--bg);color:var(--text);line-height:1.5;min-height:100dvh;}.app-shell{min-height:100dvh;display:flex;flex-direction:column;}.topbar{position:sticky;top:0;z-index:20;background:rgba(255,255,255,0.9);backdrop-filter:blur(8px);border-bottom:1px solid var(--border);padding:14px 32px;display:flex;align-items:center;justify-content:space-between;gap:24px;}.brand{display:flex;align-items:center;gap:10px;}.brand-mark{width:34px;height:34px;border-radius:10px;background:linear-gradient(135deg,var(--primary) 0%,#7c3aed 100%);color:#fff;font-size:1.25rem;font-weight:700;display:grid;place-items:center;line-height:1;}.brand-name{font-size:1.3rem;font-weight:700;letter-spacing:-0.02em;}.brand-sub{font-size:0.8125rem;color:var(--text-muted);padding-left:10px;margin-left:4px;border-left:1px solid var(--border);}.tab-switch{display:flex;gap:4px;background:var(--bg);border-radius:11px;padding:4px;}.tab-btn{padding:9px 22px;border:none;border-radius:8px;background:transparent;font-size:0.9rem;font-weight:500;color:var(--text-muted);cursor:pointer;transition:background 0.15s,color 0.15s;}.tab-btn.active{background:var(--surface);color:var(--primary);box-shadow:var(--shadow);}.subhead{display:flex;align-items:center;gap:16px;padding:22px 32px 0;max-width:calc(var(--content-max)+64px);width:100%;margin:0 auto;}.page-title{font-size:1.6rem;font-weight:700;letter-spacing:-0.01em;}.page-actions{margin-left:auto;}.main{flex:1;padding:20px 32px 48px;max-width:calc(var(--content-max)+64px);width:100%;margin:0 auto;}.page-content{max-width:var(--content-max);}.lead{color:var(--text-muted);margin-bottom:20px;font-size:0.95rem;}.hidden{display:none !important;}.btn{display:inline-flex;align-items:center;justify-content:center;gap:6px;padding:11px 18px;border:none;border-radius:var(--radius-sm);font-size:0.9rem;font-weight:600;cursor:pointer;transition:background 0.15s,opacity 0.15s,transform 0.05s;}.btn:active{transform:translateY(1px);}.btn-primary{background:var(--primary);color:#fff;}.btn-primary:hover{background:var(--primary-hover);}.btn-primary:disabled{opacity:0.7;cursor:default;}.btn-secondary{background:var(--surface);color:var(--primary);border:1px solid var(--border);}.btn-secondary:hover{background:var(--bg);}.btn-inline{width:auto;}.btn-back{padding:8px 14px;border:1px solid var(--border);border-radius:8px;background:var(--surface);font-size:0.875rem;cursor:pointer;color:var(--text);white-space:nowrap;}.btn-back:hover{background:var(--bg);}.link-btn{background:none;border:none;color:var(--primary);font-size:0.85rem;font-weight:500;cursor:pointer;padding:0;}.link-btn:hover{text-decoration:underline;}.link-btn--danger{color:var(--danger);}.card{background:var(--surface);border-radius:var(--radius);padding:20px;box-shadow:var(--shadow);border:1px solid var(--border);cursor:pointer;transition:box-shadow 0.15s,border-color 0.15s,transform 0.1s;}.card:hover{border-color:#d3d7e2;box-shadow:var(--shadow-lg);transform:translateY(-1px);}.card-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:16px;}.card-title{font-size:1.05rem;font-weight:600;margin-bottom:4px;}.card-meta{font-size:0.875rem;color:var(--text-muted);}.card-badge{display:inline-block;font-size:0.75rem;font-weight:600;padding:3px 10px;border-radius:999px;margin-right:6px;}.badge-new{background:var(--primary-soft);color:var(--primary);}.badge-viewed{background:var(--accent-bg);color:var(--accent);}.badge-deadline{background:var(--warning-bg);color:var(--warning);}.badge-overdue{background:#fee2e2;color:var(--danger);}.badge-submitted{background:var(--submitted-bg);color:var(--submitted);}.section-title{font-size:0.8rem;font-weight:700;text-transform:uppercase;letter-spacing:0.05em;color:var(--text-muted);margin:28px 0 14px;}.material-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(260px,1fr));gap:16px;}.material-grid--compact{grid-template-columns:repeat(auto-fill,minmax(220px,1fr));}.material-cell{display:flex;flex-direction:column;gap:8px;}.material-card{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);padding:18px;box-shadow:var(--shadow);height:100%;}.material-kind{display:inline-block;font-size:0.72rem;font-weight:600;color:var(--text-muted);text-transform:uppercase;letter-spacing:0.04em;margin-bottom:8px;}.material-title{font-weight:600;font-size:0.98rem;}.material-body{font-size:0.85rem;color:var(--text-muted);margin-top:6px;}.material-link{display:inline-block;margin-top:10px;color:var(--primary);font-size:0.85rem;font-weight:600;word-break:break-all;}.material-cell-actions{display:flex;gap:14px;padding-left:4px;}.material-mini-list{display:flex;flex-wrap:wrap;gap:8px;}.material-chip{background:var(--primary-soft);color:var(--primary);font-size:0.8rem;font-weight:500;padding:5px 12px;border-radius:999px;}.material-picker{display:grid;grid-template-columns:repeat(auto-fill,minmax(220px,1fr));gap:10px;margin-top:8px;}.material-pick{display:flex;align-items:center;flex-wrap:wrap;gap:6px 10px;border:1px solid var(--border);border-radius:var(--radius-sm);padding:12px 14px;cursor:pointer;background:var(--surface);transition:border-color 0.15s,background 0.15s;}.material-pick.is-checked,.material-pick:has(input:checked){border-color:var(--primary);background:var(--primary-soft);}.material-pick input{width:auto;margin:0;}.material-pick .material-kind{margin:0;width:100%;}.material-pick .material-title{font-size:0.9rem;}.student-card{display:flex;flex-direction:column;gap:12px;}.student-avatar{width:46px;height:46px;border-radius:12px;background:linear-gradient(135deg,var(--primary) 0%,#7c3aed 100%);color:#fff;font-weight:700;display:grid;place-items:center;}.student-main{flex:1;display:flex;flex-direction:column;gap:2px;}.student-main .card-badge{margin-top:6px;}.student-card-foot{border-top:1px solid var(--border);padding-top:12px;display:flex;justify-content:space-between;align-items:center;gap:12px;flex-wrap:wrap;}.share-box{display:flex;align-items:center;justify-content:space-between;gap:16px;background:var(--primary-soft);border:1px solid #dfe3fb;border-radius:var(--radius);padding:16px 20px;margin-bottom:24px;flex-wrap:wrap;}.share-label{font-size:0.78rem;font-weight:600;color:var(--primary);text-transform:uppercase;letter-spacing:0.04em;margin-bottom:4px;}.share-link{font-size:0.85rem;color:var(--text);word-break:break-all;}.profile-header{display:flex;align-items:flex-start;justify-content:space-between;gap:24px;margin-bottom:24px;padding-bottom:20px;border-bottom:1px solid var(--border);}.profile-name{font-size:1.6rem;font-weight:700;margin-bottom:6px;}.profile-note{font-size:0.92rem;color:var(--text-muted);max-width:620px;}.detail-grid{display:grid;grid-template-columns:1fr 1fr;gap:16px;}.detail-grid .detail-block--full{grid-column:1 / -1;}.detail-block{background:var(--surface);border-radius:var(--radius);padding:20px;border:1px solid var(--border);box-shadow:var(--shadow);}.detail-block h2{font-size:0.78rem;font-weight:700;color:var(--text-muted);margin-bottom:10px;text-transform:uppercase;letter-spacing:0.04em;}.detail-block p{font-size:0.95rem;white-space:pre-wrap;}.submission-block{border-color:#dfe3fb;background:#fbfbff;}.comment-block{border-left:3px solid var(--primary);}.lesson-head{display:flex;justify-content:space-between;align-items:flex-start;gap:16px;}.form-panel{max-width:680px;}.form-panel--wide{max-width:860px;}.form-grid{display:grid;grid-template-columns:1fr 1fr;gap:16px;}.form-grid .form-group--full{grid-column:1 / -1;}.form-group{margin-bottom:4px;}.form-group label{display:block;font-size:0.875rem;font-weight:600;margin-bottom:6px;}.form-group .hint{font-size:0.75rem;color:var(--text-muted);margin-top:6px;}.form-group input,.form-group textarea,.form-group select{width:100%;padding:10px 12px;border:1px solid var(--border);border-radius:var(--radius-sm);font-size:0.95rem;font-family:inherit;background:var(--surface);}.form-group input:focus,.form-group textarea:focus,.form-group select:focus{outline:none;border-color:var(--primary);box-shadow:0 0 0 3px var(--primary-soft);}.form-group textarea{min-height:100px;resize:vertical;}.form-actions{display:flex;gap:12px;margin-top:16px;}.empty-state{text-align:center;padding:60px 20px;color:var(--text-muted);background:var(--surface);border:1px dashed var(--border);border-radius:var(--radius);}.empty-title{font-size:1.1rem;font-weight:600;color:var(--text);margin-bottom:8px;}.empty-state p{margin-bottom:12px;}.student-mode .topbar{background:#ffffff;}.course-hero{background:linear-gradient(135deg,#4f46e5 0%,#7c3aed 100%);color:#fff;border-radius:20px;padding:32px;margin-bottom:12px;box-shadow:var(--shadow-lg);}.course-hero-badge{display:inline-block;font-size:0.72rem;font-weight:700;text-transform:uppercase;letter-spacing:0.06em;background:rgba(255,255,255,0.2);padding:5px 12px;border-radius:999px;margin-bottom:14px;}.course-hero-title{font-size:1.9rem;font-weight:800;letter-spacing:-0.02em;}.course-hero-desc{margin-top:10px;opacity:0.92;max-width:640px;}.progress{margin-top:22px;}.progress-bar{height:8px;background:rgba(255,255,255,0.25);border-radius:999px;overflow:hidden;}.progress-bar span{display:block;height:100%;background:#fff;border-radius:999px;transition:width 0.3s;}.progress-label{margin-top:8px;font-size:0.85rem;opacity:0.92;}.lesson-list{display:flex;flex-direction:column;gap:12px;}.lesson-row{display:flex;align-items:center;gap:16px;}.lesson-index{width:38px;height:38px;flex-shrink:0;border-radius:10px;background:var(--primary-soft);color:var(--primary);font-weight:700;display:grid;place-items:center;}.lesson-row-main{flex:1;min-width:0;}.lesson-badges{margin-top:8px;display:flex;flex-wrap:wrap;gap:6px;}.lesson-arrow{color:var(--text-muted);font-size:1.2rem;}.submission-form{margin-top:16px;display:grid;gap:12px;}.submission-form .btn{justify-self:start;}.feedback-area{margin-top:20px;padding-top:20px;border-top:1px dashed var(--border);}.ai-row{display:flex;align-items:center;gap:12px;flex-wrap:wrap;margin-bottom:10px;}.ai-hint{font-size:0.82rem;color:var(--text-muted);}.ai-status{font-size:0.82rem;color:var(--primary);min-height:1.1em;margin-bottom:8px;}.ai-status--error{color:var(--danger);}