:root{--bg:#0b0f17;--surface:#131a26;--surface-2:#1b2536;--border:#26334a;--text:#e6edf6;--muted:#93a1b4;--primary:#4f8cff;--primary-2:#3b6fd4;--accent:#38d39f;--danger:#ff5d6c;--radius:12px}*{box-sizing:border-box}body,html{padding:0;margin:0}body{background:var(--bg);color:var(--text);font-family:ui-sans-serif,system-ui,-apple-system,Segoe UI,Roboto,Noto Sans,Noto Sans TC,Noto Sans CJK TC,sans-serif;font-size:15px;line-height:1.55}a{color:var(--primary);text-decoration:none}a:hover{text-decoration:underline}h1,h2,h3{line-height:1.25}.container{max-width:1200px;margin:0 auto;padding:24px}.card{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);padding:20px}.muted{color:var(--muted)}.row{align-items:center}.col,.row{display:flex;gap:12px}.col{flex-direction:column}.grid{display:grid;grid-gap:16px;gap:16px}label{font-size:13px;color:var(--muted);display:block;margin-bottom:6px}button,input,select,textarea{font:inherit;color:var(--text);background:var(--surface-2);border:1px solid var(--border);border-radius:8px;padding:10px 12px;width:100%}textarea{resize:vertical;min-height:80px}button{width:auto;cursor:pointer;background:var(--primary);border-color:var(--primary-2);color:white;font-weight:600}button:hover{background:var(--primary-2)}button.secondary{background:var(--surface-2);color:var(--text);border-color:var(--border)}button:disabled{opacity:.5;cursor:not-allowed}.badge{display:inline-block;padding:2px 10px;border-radius:999px;font-size:12px;border:1px solid var(--border);background:var(--surface-2)}.badge.admin{color:#ffd479;border-color:#5c4a1e}.badge.moderator{color:#9ad0ff;border-color:#244a6b}.badge.teacher{color:var(--accent);border-color:#1f5a45}.badge.student{color:var(--muted)}table{width:100%;border-collapse:collapse}td,th{text-align:left;padding:10px 12px;border-bottom:1px solid var(--border)}th{color:var(--muted);font-weight:600;font-size:13px}.topbar{justify-content:space-between;padding:14px 24px;border-bottom:1px solid var(--border);background:var(--surface)}.topbar,.topbar nav{display:flex;align-items:center}.topbar nav{gap:18px}.topbar nav a{color:var(--text)}.thinking{display:inline-flex;align-items:center;gap:8px;color:var(--accent);font-weight:600}.thinking .dots{display:inline-flex;gap:3px}.thinking .dots span{width:6px;height:6px;border-radius:50%;background:var(--accent);animation:blink 1.2s ease-in-out infinite}.thinking .dots span:nth-child(2){animation-delay:.2s}.thinking .dots span:nth-child(3){animation-delay:.4s}@keyframes blink{0%,80%,to{opacity:.25}40%{opacity:1}}.split{display:grid;grid-template-columns:1fr 1fr;grid-gap:16px;gap:16px;min-height:70vh}@media (max-width:900px){.split{grid-template-columns:1fr}}.preview-frame{width:100%;height:100%;min-height:60vh;border:1px solid var(--border);border-radius:var(--radius);background:white}.chat-log{display:flex;flex-direction:column;gap:10px;overflow-y:auto;flex:1 1}.msg{padding:10px 12px;border-radius:10px;max-width:85%}.msg.user{align-self:flex-end;background:var(--primary-2)}.msg.assistant{align-self:flex-start;background:var(--surface-2);border:1px solid var(--border)}