:root{--primary: #2563eb;--primary-dark: #1d4ed8;--primary-light: #dbeafe;--bg: #f5f7fa;--card: #ffffff;--border: #e5e7eb;--text: #111827;--text-2: #6b7280;--success: #16a34a;--danger: #dc2626;--warning: #f59e0b;--radius: 12px;--shadow: 0 1px 3px rgba(0, 0, 0, .06), 0 1px 2px rgba(0, 0, 0, .04)}*{box-sizing:border-box;-webkit-tap-highlight-color:transparent}html,body,#app{margin:0;padding:0;height:100%}body{font-family:-apple-system,BlinkMacSystemFont,Segoe UI,PingFang SC,Microsoft YaHei,Helvetica Neue,sans-serif;background:var(--bg);color:var(--text);font-size:15px;line-height:1.5}.page{max-width:960px;margin:0 auto;padding:16px}.card{background:var(--card);border-radius:var(--radius);box-shadow:var(--shadow);padding:16px;border:1px solid var(--border)}.btn{-webkit-appearance:none;-moz-appearance:none;appearance:none;border:1px solid var(--border);background:#fff;color:var(--text);border-radius:8px;padding:8px 14px;font-size:14px;cursor:pointer;transition:all .15s}.btn:hover:not(:disabled){border-color:var(--primary);color:var(--primary)}.btn:disabled{opacity:.5;cursor:not-allowed}.btn-primary{background:var(--primary);border-color:var(--primary);color:#fff}.btn-primary:hover:not(:disabled){background:var(--primary-dark);color:#fff}.btn-danger{color:var(--danger);border-color:var(--danger)}.btn-block{display:block;width:100%}.btn-sm{padding:4px 10px;font-size:13px}.input,textarea.input,select.input{display:block;width:100%;border:1px solid var(--border);border-radius:8px;padding:9px 12px;font-size:15px;background:#fff;color:var(--text);outline:none}.input:focus{border-color:var(--primary);box-shadow:0 0 0 3px var(--primary-light)}.field{margin-bottom:14px}.field label{display:block;font-size:13px;color:var(--text-2);margin-bottom:6px}.tag{display:inline-block;padding:2px 10px;border-radius:999px;font-size:12px;border:1px solid var(--border);color:var(--text-2)}.tag-blue{background:var(--primary-light);color:var(--primary);border-color:transparent}.tag-green{background:#dcfce7;color:var(--success);border-color:transparent}.tag-gray{background:#f3f4f6;border-color:transparent}.tag-red{background:#fee2e2;color:var(--danger);border-color:transparent}.navbar{display:flex;align-items:center;justify-content:space-between;padding:10px 16px;background:#fff;border-bottom:1px solid var(--border);position:sticky;top:0;z-index:50}.navbar .brand{font-weight:700;color:var(--primary);font-size:17px;text-decoration:none}.row{display:flex;gap:10px;align-items:center}.grow{flex:1}.muted{color:var(--text-2);font-size:13px}.empty{text-align:center;color:var(--text-2);padding:40px 0}#toast-wrap{position:fixed;top:16px;left:50%;transform:translate(-50%);z-index:999;display:flex;flex-direction:column;gap:8px;width:max-content;max-width:90vw}.toast-item{background:#111827eb;color:#fff;padding:10px 18px;border-radius:8px;font-size:14px;animation:toast-in .2s ease}@keyframes toast-in{0%{opacity:0;transform:translateY(-8px)}to{opacity:1;transform:none}}.modal-mask{position:fixed;top:0;right:0;bottom:0;left:0;background:#00000073;z-index:100;display:flex;align-items:center;justify-content:center;padding:16px}.modal{background:#fff;border-radius:14px;width:100%;max-width:560px;max-height:88vh;overflow:auto;padding:20px;animation:toast-in .18s ease}.classroom-layout{display:flex;flex-direction:column;height:100dvh;background:#eef1f5}.classroom-body{flex:1;display:flex;flex-direction:column;min-height:0}.ppt-pane{flex:1;min-height:0;display:flex;align-items:center;justify-content:center;background:#1f2937;position:relative;overflow:hidden}.ppt-pane img{max-width:100%;max-height:100%;object-fit:contain}.note-pane{height:42vh;display:flex;flex-direction:column;border-top:1px solid var(--border);background:#fff}@media (min-width: 768px) and (orientation: landscape){.classroom-body{flex-direction:row}.ppt-pane{flex:1.5}.note-pane{height:auto;flex:1;border-top:none;border-left:1px solid var(--border)}}.note-editor-wrap{flex:1;min-height:0}.classroom-topbar{display:flex;align-items:center;gap:8px;padding:8px 12px;background:#fff;border-bottom:1px solid var(--border);flex-wrap:nowrap;overflow-x:auto}.banner-follow{background:var(--warning);color:#fff;padding:6px 12px;text-align:center;font-size:13px;cursor:pointer;flex-shrink:0}.option-item{display:flex;align-items:center;gap:10px;padding:12px;border:2px solid var(--border);border-radius:10px;margin-bottom:10px;cursor:pointer;font-size:15px}.option-item.selected{border-color:var(--primary);background:var(--primary-light)}.option-key{width:28px;height:28px;border-radius:50%;background:#f3f4f6;display:flex;align-items:center;justify-content:center;font-weight:600;flex-shrink:0}.bar-row{display:flex;align-items:center;gap:8px;margin-bottom:6px;font-size:13px}.bar-row .bar-label{width:70px;flex-shrink:0;text-align:right;color:var(--text-2)}.bar-row .bar-track{flex:1;background:#f3f4f6;border-radius:4px;height:18px;overflow:hidden}.bar-row .bar-fill{height:100%;background:var(--primary);border-radius:4px;transition:width .3s}.bar-row .bar-fill.correct{background:var(--success)}.bar-row .bar-count{width:36px;flex-shrink:0}.member-item{display:flex;justify-content:space-between;align-items:center;padding:10px 4px;border-bottom:1px solid var(--border);cursor:pointer}.list-plain{list-style:none;margin:0;padding:0}