:root{--primary: #52B991;--primary-d: #3a9b7a;--primary-bg: #E6F8F2;--blue: #1677FF;--orange: #F0995C;--red: #FF6B6B;--yellow: #F6C84B;--text: #1a1a2e;--text-2: #555;--text-3: #999;--border: #E4E6F0;--bg: #F0F2F5;--card: #FFFFFF;--sidebar: #1a2332;--sidebar-hover: rgba(255,255,255,.07);--sidebar-active: rgba(82,185,145,.18);--header-h: 60px;--sidebar-w: 220px;--radius: 12px;--radius-sm: 8px;--shadow: 0 2px 12px rgba(0,0,0,.07);--shadow-lg: 0 8px 32px rgba(0,0,0,.14)}*,*:before,*:after{box-sizing:border-box;margin:0;padding:0}body{font-family:-apple-system,PingFang SC,Microsoft YaHei,sans-serif;background:var(--bg);color:var(--text);font-size:14px;line-height:1.6}a{color:inherit;text-decoration:none}.app-layout{display:flex;height:100vh;overflow:hidden}.sidebar{width:var(--sidebar-w);flex-shrink:0;background:var(--sidebar);display:flex;flex-direction:column;overflow-y:auto}.sidebar-logo{padding:20px 20px 16px;border-bottom:1px solid rgba(255,255,255,.08)}.sidebar-logo h1{color:#fff;font-size:18px;font-weight:800}.sidebar-logo h1 span{color:var(--primary)}.sidebar-logo p{color:#fff6;font-size:11px;margin-top:2px}.sidebar-nav{flex:1;padding:10px 0}.nav-item{display:flex;align-items:center;gap:10px;padding:11px 20px;color:#fff9;cursor:pointer;transition:background .15s,color .15s;font-size:14px;border-left:3px solid transparent}.nav-item:hover{background:var(--sidebar-hover);color:#ffffffe6}.nav-item.active{background:var(--sidebar-active);color:var(--primary);border-left-color:var(--primary)}.nav-item-icon{font-size:16px;width:20px;text-align:center}.sidebar-footer{padding:14px 20px;border-top:1px solid rgba(255,255,255,.08)}.user-chip{display:flex;align-items:center;gap:10px}.user-avatar{width:34px;height:34px;border-radius:50%;background:var(--primary);display:flex;align-items:center;justify-content:center;color:#fff;font-size:15px;font-weight:700;flex-shrink:0}.user-info{flex:1;overflow:hidden;min-width:0}.user-name{color:#ffffffe6;font-size:13px;font-weight:600;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}.user-role{color:#fff6;font-size:11px}.logout-btn{color:#ffffff59;cursor:pointer;font-size:12px;margin-top:6px;transition:color .15s}.logout-btn:hover{color:var(--red)}.main-area{flex:1;overflow-y:auto;display:flex;flex-direction:column;min-width:0}.page-header{background:var(--card);border-bottom:1px solid var(--border);padding:0 28px;height:var(--header-h);display:flex;align-items:center;justify-content:space-between;flex-shrink:0;position:sticky;top:0;z-index:10}.page-title{font-size:17px;font-weight:700}.header-actions{display:flex;gap:8px;align-items:center}.page-body{flex:1;padding:24px 28px}.btn{display:inline-flex;align-items:center;justify-content:center;gap:6px;padding:8px 18px;border-radius:var(--radius-sm);border:none;cursor:pointer;font-size:14px;font-weight:500;transition:opacity .15s,transform .1s;white-space:nowrap;font-family:inherit}.btn:active{transform:scale(.97)}.btn:disabled{opacity:.5;cursor:not-allowed}.btn-primary{background:var(--primary);color:#fff}.btn-primary:hover:not(:disabled){background:var(--primary-d)}.btn-blue{background:var(--blue);color:#fff}.btn-blue:hover:not(:disabled){opacity:.9}.btn-outline{background:transparent;color:var(--text-2);border:1.5px solid var(--border)}.btn-outline:hover:not(:disabled){border-color:var(--primary);color:var(--primary)}.btn-danger{background:var(--red);color:#fff}.btn-danger:hover:not(:disabled){opacity:.88}.btn-ghost{background:transparent;color:var(--text-3);border:none;padding:6px 10px}.btn-ghost:hover{color:var(--primary)}.btn-sm{padding:5px 12px;font-size:12px}.btn-lg{padding:12px 28px;font-size:16px}.btn-block{width:100%}.card{background:var(--card);border-radius:var(--radius);box-shadow:var(--shadow);padding:20px}.card-header{display:flex;align-items:center;justify-content:space-between;margin-bottom:16px}.card-title{font-size:15px;font-weight:600}.form-group{margin-bottom:16px}.form-label{display:block;font-size:13px;color:var(--text-2);font-weight:500;margin-bottom:6px}.form-input,.form-textarea,.form-select{width:100%;padding:10px 14px;border:1.5px solid var(--border);border-radius:var(--radius-sm);font-size:14px;color:var(--text);background:#fff;transition:border-color .15s;font-family:inherit;outline:none}.form-input:focus,.form-textarea:focus,.form-select:focus{border-color:var(--primary)}.form-textarea{resize:vertical;min-height:100px}.form-hint{font-size:12px;color:var(--text-3);margin-top:4px}.input-with-btn{display:flex;gap:8px}.input-with-btn .form-input{flex:1}.table-wrap{overflow-x:auto;border-radius:var(--radius);background:var(--card);box-shadow:var(--shadow)}table{width:100%;border-collapse:collapse}th{background:#f8fafc;padding:11px 16px;text-align:left;font-size:13px;color:var(--text-3);font-weight:600;border-bottom:1px solid var(--border)}td{padding:12px 16px;font-size:14px;border-bottom:1px solid var(--border)}tr:last-child td{border-bottom:none}tbody tr:hover td{background:#fafbfc}.badge{display:inline-flex;align-items:center;padding:3px 10px;border-radius:999px;font-size:12px;font-weight:600}.badge-green{background:var(--primary-bg);color:var(--primary)}.badge-blue{background:#eef4ff;color:var(--blue)}.badge-red{background:#fff0f0;color:var(--red)}.badge-orange{background:#fff3e6;color:var(--orange)}.badge-gray{background:#f0f2f5;color:var(--text-3)}.badge-yellow{background:#fff8e0;color:#b8870a}.stat-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(190px,1fr));gap:16px;margin-bottom:24px}.stat-card{background:var(--card);border-radius:var(--radius);box-shadow:var(--shadow);padding:20px;display:flex;align-items:center;gap:14px}.stat-icon{width:46px;height:46px;border-radius:14px;display:flex;align-items:center;justify-content:center;font-size:22px;flex-shrink:0}.stat-num{font-size:26px;font-weight:700;line-height:1.2}.stat-label{font-size:12px;color:var(--text-3);margin-top:2px}.empty{display:flex;flex-direction:column;align-items:center;justify-content:center;padding:60px 20px;color:var(--text-3)}.empty-icon{font-size:44px;margin-bottom:12px}.empty-text{font-size:14px}.modal-overlay{position:fixed;top:0;right:0;bottom:0;left:0;background:#0000006b;z-index:1000;display:flex;align-items:center;justify-content:center}.modal{background:#fff;border-radius:var(--radius);box-shadow:var(--shadow-lg);width:90%;max-width:520px;max-height:90vh;overflow-y:auto}.modal-lg{max-width:680px}.modal-header{display:flex;align-items:center;justify-content:space-between;padding:20px 24px 0}.modal-title{font-size:16px;font-weight:700}.modal-close{cursor:pointer;font-size:22px;color:var(--text-3);line-height:1}.modal-close:hover{color:var(--text)}.modal-body{padding:20px 24px}.modal-footer{padding:0 24px 20px;display:flex;gap:10px;justify-content:flex-end}.login-page{min-height:100vh;background:linear-gradient(135deg,#1a2332,#243447);display:flex;align-items:center;justify-content:center}.login-card{background:#fff;border-radius:20px;box-shadow:0 20px 60px #0000004d;padding:40px;width:400px;max-width:92vw}.login-logo{text-align:center;margin-bottom:28px}.login-logo h1{font-size:26px;font-weight:800}.login-logo h1 span{color:var(--primary)}.login-logo p{color:var(--text-3);font-size:13px;margin-top:4px}.tab-bar{display:flex;border-bottom:2px solid var(--border);margin-bottom:20px}.tab{padding:10px 20px;cursor:pointer;font-size:14px;color:var(--text-3);border-bottom:2px solid transparent;margin-bottom:-2px;transition:color .15s}.tab:hover{color:var(--text)}.tab.active{color:var(--primary);border-bottom-color:var(--primary);font-weight:600}.progress-bar{height:8px;border-radius:4px;background:var(--border);overflow:hidden}.progress-fill{height:100%;border-radius:4px;background:var(--primary);transition:width .3s}@keyframes spin{to{transform:rotate(360deg)}}.spinner{display:inline-block;width:18px;height:18px;border:2px solid var(--border);border-top-color:var(--primary);border-radius:50%;animation:spin .6s linear infinite}.loading-center{display:flex;justify-content:center;align-items:center;padding:60px}.class-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:16px}.class-card{background:var(--card);border-radius:var(--radius);box-shadow:var(--shadow);padding:20px;border-top:4px solid var(--primary);transition:transform .15s,box-shadow .15s}.class-card:hover{transform:translateY(-2px);box-shadow:var(--shadow-lg)}.class-name{font-size:16px;font-weight:700}.class-meta{font-size:13px;color:var(--text-3);margin-top:4px}.invite-row{display:flex;align-items:center;gap:8px;background:var(--bg);border-radius:8px;padding:8px 12px;margin-top:12px}.invite-code{font-size:20px;font-weight:800;letter-spacing:4px;color:var(--primary);flex:1}.resource-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(220px,1fr));gap:14px}.resource-card{background:var(--card);border-radius:var(--radius);box-shadow:var(--shadow);padding:16px;transition:transform .15s;cursor:pointer}.resource-card:hover{transform:translateY(-2px);box-shadow:var(--shadow-lg)}.res-name{font-weight:600;font-size:14px;margin:8px 0 4px;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}.res-meta{font-size:12px;color:var(--text-3)}.messages-wrap{display:flex;background:var(--card);border-radius:var(--radius);box-shadow:var(--shadow);overflow:hidden;height:calc(100vh - var(--header-h) - 48px)}.conv-list{width:260px;border-right:1px solid var(--border);overflow-y:auto;flex-shrink:0}.conv-item{padding:14px 16px;cursor:pointer;border-bottom:1px solid var(--border);transition:background .15s}.conv-item:hover{background:#f8fafc}.conv-item.active{background:var(--primary-bg)}.conv-name{font-weight:600;font-size:14px}.conv-preview{font-size:12px;color:var(--text-3);margin-top:2px}.chat-area{flex:1;display:flex;flex-direction:column;min-width:0}.chat-messages{flex:1;overflow-y:auto;padding:16px;display:flex;flex-direction:column;gap:10px}.chat-bubble{max-width:62%;padding:9px 14px;border-radius:12px;font-size:14px;line-height:1.5}.chat-bubble.me{background:var(--primary);color:#fff;align-self:flex-end;border-bottom-right-radius:3px}.chat-bubble.other{background:#f0f2f5;color:var(--text);align-self:flex-start;border-bottom-left-radius:3px}.chat-time{font-size:11px;opacity:.6;margin-top:3px}.chat-input-row{display:flex;gap:8px;padding:12px 16px;border-top:1px solid var(--border)}.chat-input-row .form-input{flex:1}.hw-item{display:flex;align-items:center;gap:14px;padding:14px 20px;background:var(--card);border-radius:var(--radius);box-shadow:var(--shadow);cursor:pointer;transition:transform .12s;margin-bottom:10px}.hw-item:hover{transform:translate(2px)}.hw-title{font-weight:600;font-size:15px}.hw-meta{font-size:13px;color:var(--text-3);margin-top:2px}.hw-progress{flex:1;min-width:80px;max-width:140px}.book-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(200px,1fr));gap:16px}.book-card{background:var(--card);border-radius:var(--radius);box-shadow:var(--shadow);overflow:hidden;cursor:pointer;transition:transform .15s}.book-card:hover{transform:translateY(-3px);box-shadow:var(--shadow-lg)}.book-cover{height:120px;display:flex;align-items:center;justify-content:center;font-size:48px}.book-info{padding:12px}.book-title{font-weight:600;font-size:14px}.book-sub{font-size:12px;color:var(--text-3);margin-top:2px}.flex{display:flex}.flex-1{flex:1}.items-center{align-items:center}.justify-between{justify-content:space-between}.gap-2{gap:8px}.gap-3{gap:12px}.mb-3{margin-bottom:12px}.mb-4{margin-bottom:16px}.mb-6{margin-bottom:24px}.mt-2{margin-top:8px}.text-sm{font-size:13px}.text-xs{font-size:12px}.text-muted{color:var(--text-3)}.text-primary{color:var(--primary)}.font-bold{font-weight:700}.divider{height:1px;background:var(--border);margin:16px 0}.row{display:flex;gap:16px;align-items:flex-start}.col-2{display:grid;grid-template-columns:1fr 1fr;gap:16px}.toast-container{position:fixed;top:20px;right:20px;z-index:9999;display:flex;flex-direction:column;gap:8px;pointer-events:none}.toast{padding:12px 18px;border-radius:10px;font-size:14px;font-weight:500;box-shadow:var(--shadow-lg);animation:slideIn .2s ease}.toast-success{background:var(--primary);color:#fff}.toast-error{background:var(--red);color:#fff}@keyframes slideIn{0%{opacity:0;transform:translate(20px)}to{opacity:1;transform:translate(0)}}.class-checkboxes{display:grid;grid-template-columns:1fr 1fr;gap:8px}.class-checkbox-item{display:flex;align-items:center;gap:8px;cursor:pointer;padding:8px 12px;border:1.5px solid var(--border);border-radius:var(--radius-sm);transition:all .15s}.class-checkbox-item.selected{border-color:var(--primary);background:var(--primary-bg);color:var(--primary)}.class-checkbox-item input{display:none}.due-presets{display:flex;gap:8px;flex-wrap:wrap;margin-bottom:8px}.due-preset{padding:6px 12px;border:1.5px solid var(--border);border-radius:999px;font-size:13px;cursor:pointer;transition:all .15s}.due-preset:hover,.due-preset.active{border-color:var(--primary);background:var(--primary-bg);color:var(--primary)}.upload-area{border:2px dashed var(--border);border-radius:var(--radius);padding:24px;text-align:center;cursor:pointer;transition:border-color .15s}.upload-area:hover{border-color:var(--primary)}.upload-area input{display:none}.attached-file{display:flex;align-items:center;gap:8px;padding:8px 12px;background:var(--bg);border-radius:var(--radius-sm);margin-top:8px}.book-page{max-width:700px;margin:0 auto}.book-page-text{font-size:18px;line-height:1.8;margin-bottom:16px;color:var(--text)}.book-page-en{font-size:22px;font-weight:600;color:var(--primary-d)}.page-nav{display:flex;align-items:center;justify-content:center;gap:20px;padding:20px 0}