:root {
  --bg: #f5f6f8;
  --panel: #ffffff;
  --side: #f0f2f5;
  --border: #e2e5ea;
  --text: #1f2329;
  --muted: #6b7380;
  --primary: #2563eb;
  --primary-soft: #e8efff;
  --ask: #d97706;
  --ask-soft: #fff4e0;
  --ok: #15803d;
  --ok-soft: #e7f6ec;
  --danger: #dc2626;
  --radius: 10px;
  --font: -apple-system, "PingFang SC", "Microsoft YaHei", "Noto Sans SC", "Segoe UI", sans-serif;
}

* { box-sizing: border-box; }
html, body { height: 100%; margin: 0; }
body { font: 15px/1.6 var(--font); color: var(--text); background: var(--bg); }
button, input, textarea { font: inherit; color: inherit; }
.hidden { display: none !important; }
.boot { display: grid; place-items: center; height: 100%; color: var(--muted); }

/* ---------- 按钮 ---------- */
.btn {
  border: 1px solid var(--border); background: var(--panel); border-radius: 8px;
  padding: 7px 16px; cursor: pointer; white-space: nowrap;
}
.btn:hover:not(:disabled) { border-color: #c5cad3; }
.btn:disabled { opacity: .5; cursor: not-allowed; }
.btn.primary { background: var(--primary); border-color: var(--primary); color: #fff; }
.btn.primary:hover:not(:disabled) { background: #1d4ed8; }
.btn.ask { background: var(--ask); border-color: var(--ask); color: #fff; font-weight: 600; }
.btn.ask:hover:not(:disabled) { background: #b45309; }
.btn.block { display: block; width: 100%; }
.link { border: 0; background: none; color: var(--primary); cursor: pointer; padding: 0 2px; }
.icon-btn { border: 0; background: none; font-size: 20px; cursor: pointer; padding: 0 6px; }

/* ---------- 登录 ---------- */
.auth { min-height: 100%; display: grid; place-items: center; padding: 24px 16px; }
.auth-card { width: 100%; max-width: 380px; background: var(--panel); border: 1px solid var(--border); border-radius: 14px; padding: 28px; }
.auth-card h1 { margin: 0 0 18px; font-size: 22px; text-align: center; }
.form { display: grid; gap: 12px; }
.form label { display: grid; gap: 4px; font-size: 13px; color: var(--muted); }
.form input:not([type=radio]) { border: 1px solid var(--border); border-radius: 8px; padding: 8px 10px; font-size: 15px; color: var(--text); }
.form input:focus, textarea:focus { outline: 2px solid var(--primary-soft); border-color: var(--primary); }
.role-pick { display: flex; gap: 20px; }
.role-pick label { display: flex; align-items: center; gap: 6px; color: var(--text); font-size: 15px; }
.form-error { color: var(--danger); margin: 0; min-height: 1em; font-size: 13px; }

.tabs { display: flex; gap: 4px; border-bottom: 1px solid var(--border); margin-bottom: 16px; }
.tab { border: 0; background: none; padding: 8px 14px; cursor: pointer; color: var(--muted); border-bottom: 2px solid transparent; margin-bottom: -1px; }
.tab.active { color: var(--primary); border-bottom-color: var(--primary); font-weight: 600; }
.tabs.small { margin: 0 0 8px; }
.tabs.small .tab { padding: 6px 10px; font-size: 14px; }
.count { color: var(--ask); font-weight: 700; }

/* ---------- 应用框架 ---------- */
.app { display: flex; height: 100%; }
.sidebar {
  width: 260px; flex-shrink: 0; background: var(--side); border-right: 1px solid var(--border);
  display: flex; flex-direction: column; padding: 14px 12px; gap: 10px; min-height: 0;
}
.sidebar.wide { width: 330px; }
.brand { font-weight: 700; font-size: 16px; padding: 2px 4px 6px; }
.list { flex: 1; overflow-y: auto; display: flex; flex-direction: column; gap: 2px; min-height: 0; }
.list-item {
  display: block; width: 100%; text-align: left; border: 0; background: none; border-radius: 8px;
  padding: 8px 10px; cursor: pointer; color: var(--text);
}
.list-item:hover { background: #e4e7ec; }
.list-item.active { background: var(--panel); box-shadow: 0 0 0 1px var(--border); }
.list-item .title { display: block; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.list-item .meta { display: flex; justify-content: space-between; gap: 8px; font-size: 12px; color: var(--muted); }
.list-item .snippet { font-size: 13px; color: var(--muted); display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden; }
.conv-row { display: flex; align-items: center; border-radius: 8px; }
.conv-row .list-item { flex: 1; min-width: 0; }
.conv-row .del { visibility: hidden; border: 0; background: none; color: var(--muted); cursor: pointer; padding: 4px 8px; }
.conv-row:hover .del { visibility: visible; }
.conv-row .del:hover { color: var(--danger); }
.list-empty { color: var(--muted); font-size: 13px; padding: 8px 10px; }

.sidebar-foot { border-top: 1px solid var(--border); padding-top: 8px; display: grid; gap: 6px; }
.side-link { text-align: left; border: 0; background: none; padding: 6px 10px; border-radius: 8px; cursor: pointer; display: flex; align-items: center; gap: 6px; }
.side-link:hover, .side-link.active { background: #e4e7ec; }
.badge { background: var(--danger); color: #fff; border-radius: 999px; font-size: 12px; padding: 0 7px; line-height: 18px; }
.me { display: flex; justify-content: space-between; align-items: center; padding: 0 10px; font-size: 13px; color: var(--muted); }

.class-code { background: var(--panel); border: 1px solid var(--border); border-radius: 8px; padding: 8px 10px; }
.class-code strong { font-size: 18px; letter-spacing: 2px; color: var(--primary); }
.class-code small { color: var(--muted); }

.main { flex: 1; min-width: 0; display: flex; flex-direction: column; background: var(--panel); }
.pane { flex: 1; display: flex; flex-direction: column; min-height: 0; }
.pane-head { display: flex; align-items: center; gap: 10px; padding: 12px 20px; border-bottom: 1px solid var(--border); }
.pane-head h2 { flex: 1; margin: 0; font-size: 16px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.menu-btn { display: none; }
.scroll-body { flex: 1; overflow-y: auto; padding: 20px; }
.banner { background: var(--ask-soft); color: #8a4b00; font-size: 13px; padding: 6px 20px; border-bottom: 1px solid #f5ddb5; }
.empty { color: var(--muted); text-align: center; margin-top: 15vh; }

/* ---------- 聊天 ---------- */
.messages { flex: 1; overflow-y: auto; padding: 24px 20px; display: flex; flex-direction: column; gap: 18px; }
.welcome { margin: auto; text-align: center; color: var(--muted); max-width: 420px; }
.welcome h3 { color: var(--text); margin: 0 0 8px; }
.msg { display: flex; flex-direction: column; max-width: 780px; width: 100%; margin: 0 auto; }
.msg .who { font-size: 12px; color: var(--muted); margin-bottom: 4px; }
.msg.user { align-items: flex-end; }
.msg.user .bubble { background: var(--primary-soft); border-radius: 14px 14px 4px 14px; padding: 8px 14px; white-space: pre-wrap; word-break: break-word; max-width: 85%; }
.msg.assistant .bubble { word-break: break-word; }
.msg .tools { margin-top: 4px; opacity: 0; transition: opacity .15s; }
.msg:hover .tools, .msg .tools:focus-within { opacity: 1; }
.msg .tools button { font-size: 12px; border: 1px solid var(--border); background: var(--panel); border-radius: 6px; padding: 2px 8px; cursor: pointer; color: var(--ask); }
.msg.quoted .bubble { outline: 2px solid var(--ask); outline-offset: 4px; border-radius: 6px; }
.typing::after { content: "▍"; animation: blink 1s steps(2) infinite; color: var(--muted); }
.typing:empty::after { content: "思考中…"; animation: pulse 1.6s ease-in-out infinite; }
@keyframes pulse { 50% { opacity: .35; } }
@keyframes blink { 50% { opacity: 0; } }

.markdown h1, .markdown h2, .markdown h3, .markdown h4 { line-height: 1.4; margin: 1em 0 .4em; }
.markdown h1 { font-size: 1.25em; }
.markdown h2 { font-size: 1.15em; }
.markdown h3, .markdown h4 { font-size: 1.05em; }
.markdown hr { border: 0; border-top: 1px solid var(--border); margin: 12px 0; }
.markdown > :first-child { margin-top: 0; }
.markdown > :last-child { margin-bottom: 0; }
.markdown pre { background: #f6f8fa; border: 1px solid var(--border); border-radius: 8px; padding: 10px 12px; overflow-x: auto; font-size: 13px; }
.markdown code { font-family: Consolas, "SFMono-Regular", Menlo, monospace; font-size: .92em; }
.markdown :not(pre) > code { background: #f0f2f5; padding: 1px 5px; border-radius: 4px; }
.markdown blockquote { margin: 8px 0; padding: 2px 12px; border-left: 3px solid var(--border); color: var(--muted); }
.markdown .math-block { margin: 10px 0; overflow-x: auto; overflow-y: hidden; }
.markdown .katex { font-size: 1.08em; }
.markdown .katex-error { color: var(--danger); }
.markdown table { border-collapse: collapse; }
.markdown th, .markdown td { border: 1px solid var(--border); padding: 4px 10px; }

/* 对话里的"问老师"记录 */
.qcard { max-width: 780px; width: 100%; margin: 0 auto; border: 1px solid #f0d3a2; background: var(--ask-soft); border-radius: var(--radius); padding: 10px 14px; font-size: 14px; }
.qcard .label { font-size: 12px; font-weight: 600; color: var(--ask); }
.qcard .q { white-space: pre-wrap; margin: 2px 0 6px; }
.qcard .reply { background: var(--panel); border-radius: 8px; padding: 8px 12px; border: 1px solid var(--border); }
.qcard .reply .label { color: var(--ok); }
.qcard .pending { color: var(--muted); font-size: 13px; }

.composer { display: flex; gap: 10px; align-items: flex-end; padding: 12px 20px 16px; border-top: 1px solid var(--border); max-width: 820px; width: 100%; margin: 0 auto; }
.composer textarea { flex: 1; resize: none; border: 1px solid var(--border); border-radius: 10px; padding: 9px 12px; max-height: 200px; line-height: 1.5; overflow-y: hidden; }

/* ---------- 提问卡片（学生"我的提问"） ---------- */
.qitem { border: 1px solid var(--border); border-radius: var(--radius); padding: 12px 16px; margin: 0 auto 12px; max-width: 780px; }
.qitem.unseen { border-color: var(--ok); box-shadow: 0 0 0 1px var(--ok); }
.qitem-head { display: flex; justify-content: space-between; gap: 10px; font-size: 13px; color: var(--muted); margin-bottom: 6px; }
.status { font-size: 12px; border-radius: 999px; padding: 1px 8px; }
.status.open { background: var(--ask-soft); color: var(--ask); }
.status.answered { background: var(--ok-soft); color: var(--ok); }
.qitem .q { white-space: pre-wrap; margin-bottom: 8px; }
.qitem .reply { background: var(--ok-soft); border-radius: 8px; padding: 8px 12px; }

/* ---------- 教师详情 ---------- */
.detail { max-width: 860px; margin: 0 auto; display: grid; gap: 18px; }
.detail-meta { color: var(--muted); font-size: 13px; display: flex; flex-wrap: wrap; gap: 6px 16px; align-items: center; }
.section-title { font-size: 13px; font-weight: 600; color: var(--muted); margin: 0 0 8px; }
.question-box { background: var(--ask-soft); border: 1px solid #f0d3a2; border-radius: var(--radius); padding: 12px 16px; }
.question-box .q { white-space: pre-wrap; font-size: 16px; }
.quote { border-left: 3px solid var(--ask); padding: 4px 10px; margin-top: 10px; font-size: 13px; color: var(--muted); background: rgba(255,255,255,.6); border-radius: 0 6px 6px 0; }
.quote .markdown { max-height: 120px; overflow: hidden; }
.transcript { border: 1px solid var(--border); border-radius: var(--radius); padding: 16px; display: flex; flex-direction: column; gap: 16px; max-height: 60vh; overflow-y: auto; background: #fbfbfc; }
.transcript .msg .tools { display: none; }
.reply-box textarea { width: 100%; min-height: 110px; border: 1px solid var(--border); border-radius: 10px; padding: 10px 12px; resize: vertical; }
.reply-actions { display: flex; justify-content: flex-end; gap: 10px; margin-top: 8px; }
.answered-reply { background: var(--ok-soft); border-radius: var(--radius); padding: 12px 16px; }

table.students { width: 100%; border-collapse: collapse; font-size: 14px; }
table.students th, table.students td { text-align: left; padding: 8px 10px; border-bottom: 1px solid var(--border); }
table.students th { color: var(--muted); font-weight: 600; }

/* ---------- 弹窗 / 提示 ---------- */
.modal { position: fixed; inset: 0; background: rgba(15, 23, 42, .4); display: grid; place-items: center; padding: 16px; z-index: 50; }
.modal-card { background: var(--panel); border-radius: 14px; width: 100%; max-width: 560px; padding: 22px; max-height: 90vh; overflow-y: auto; }
.modal-card h3 { margin: 0 0 12px; }
.modal-card textarea { width: 100%; min-height: 120px; border: 1px solid var(--border); border-radius: 10px; padding: 10px 12px; resize: vertical; }
.modal-card .hint { color: var(--muted); font-size: 13px; margin: 8px 0 0; }
.modal-card .actions { display: flex; justify-content: flex-end; gap: 10px; margin-top: 16px; }
.toast { position: fixed; left: 50%; bottom: 96px; transform: translateX(-50%); background: #1f2329; color: #fff; padding: 8px 18px; border-radius: 8px; z-index: 60; font-size: 14px; max-width: calc(100% - 32px); }
.toast.error { background: var(--danger); }

/* ---------- 窄屏 ---------- */
.scrim { display: none; }
@media (max-width: 760px) {
  .sidebar, .sidebar.wide { position: fixed; inset: 0 auto 0 0; width: 84%; max-width: 330px; z-index: 40; transform: translateX(-100%); transition: transform .2s; }
  .app.sidebar-open .sidebar { transform: none; }
  .app.sidebar-open .scrim { display: block; position: fixed; inset: 0; background: rgba(15, 23, 42, .35); z-index: 30; }
  .menu-btn { display: block; }
  .pane-head { padding: 10px 12px; }
  .messages, .scroll-body { padding: 16px; }
  .composer { padding: 10px 16px 14px; }
  .msg .tools { opacity: 1; }
}