:root {
  --fg: #0f172a;
  --fg2: #334155;
  --muted: #64748b;
  --line: #e6e9f0;
  --soft: #f8fafc;
  --accent: #2563eb;
  --accent-d: #1d4ed8;
  --accent-soft: #eff6ff;
  --ok: #059669;
  --warn: #b45309;
  --bad: #dc2626;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, "Cascadia Mono", monospace;
  --radius: 12px;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  background: #fff;
  color: var(--fg);
  font: 15px/1.75 -apple-system, BlinkMacSystemFont, "Segoe UI", "Microsoft YaHei", system-ui, sans-serif;
  -webkit-font-smoothing: antialiased;
}

a { color: inherit; text-decoration: none; transition: color .12s; }
a:hover { color: var(--accent); }
a.u { font-weight: 500; }
a.u:hover { color: var(--accent); }

::selection { background: #dbeafe; }

/* ---------------- 顶栏 ---------------- */
.topbar {
  position: sticky; top: 0; z-index: 50;
  display: flex; align-items: center; gap: 24px;
  height: 58px; padding: 0 24px;
  background: rgba(255,255,255,.86);
  backdrop-filter: saturate(180%) blur(12px);
  border-bottom: 1px solid var(--line);
}
.topbar::before {
  content: ''; position: absolute; inset: 0 0 auto 0; height: 3px;
  background: linear-gradient(90deg, #2563eb, #7c3aed 45%, #06b6d4);
}
.brand { font-weight: 800; font-size: 16.5px; letter-spacing: -.2px; display: flex; align-items: center; gap: 8px; }
.brand::before {
  content: '</>'; font-family: var(--mono); font-size: 12px; font-weight: 700;
  color: #fff; background: linear-gradient(135deg, #2563eb, #7c3aed);
  padding: 3px 7px; border-radius: 7px; letter-spacing: 0;
}
.nav { display: flex; gap: 4px; font-size: 14.5px; }
.nav a { padding: 6px 12px; border-radius: 8px; color: var(--fg2); }
.nav a:hover { background: var(--soft); color: var(--fg); }
.nav a.active { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
.userbox { display: flex; align-items: center; gap: 10px; font-size: 14px; margin-left: auto; }
.me { display: flex; align-items: center; gap: 7px; color: var(--fg2); }
.admin-btn { border-color: #ddd6fe; background: #f5f3ff; color: #6d28d9; }
.admin-btn:hover { border-color: #a78bfa; color: #6d28d9; }

/* ---------------- 布局 ---------------- */
.container { max-width: 1080px; margin: 0 auto; padding: 28px 24px 90px; }
.pagehead { display: flex; align-items: baseline; gap: 14px; margin-bottom: 18px; }
.pagehead h1 { font-size: 24px; }
h1 { font-size: 24px; margin: 0; letter-spacing: -.3px; }
h2 { font-size: 16px; margin: 0 0 12px; letter-spacing: -.1px; }
.sub { color: var(--muted); font-size: 13.5px; }
.row-head { display: flex; align-items: center; gap: 10px; }

.card {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 20px 22px;
  margin-bottom: 18px;
  background: #fff;
  transition: border-color .15s, box-shadow .15s;
}
.card:hover { border-color: #d7dced; box-shadow: 0 2px 14px rgba(15,23,42,.045); }
.card.tight { padding: 10px 12px; }
.card-actions { display: flex; gap: 10px; align-items: center; margin-top: 16px; }
.two-col { display: grid; grid-template-columns: 1fr 1fr; gap: 26px; align-items: start; }

.grid2 { display: grid; grid-template-columns: 1fr 1fr; gap: 18px; }
.grid4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: 14px; }

/* ---------------- 首页 hero ---------------- */
.hero {
  position: relative; overflow: hidden;
  display: grid; grid-template-columns: 1.5fr 1fr; gap: 26px; align-items: center;
  border: 1px solid var(--line); border-radius: 14px;
  padding: 22px 26px;
  margin-bottom: 16px;
  background:
    radial-gradient(900px 300px at 8% -20%, #eef4ff 0%, rgba(255,255,255,0) 62%),
    radial-gradient(700px 260px at 96% 130%, #f3f0ff 0%, rgba(255,255,255,0) 60%),
    #fff;
}
.hero h1 { font-size: 25px; letter-spacing: -.6px; margin-bottom: 7px; }
.hero p { color: var(--fg2); margin: 0 0 14px; max-width: 46ch; font-size: 14px; }
.hero-actions { display: flex; gap: 9px; }
.hero-stats { display: grid; grid-template-columns: 1fr 1fr; gap: 9px; }
.hero-stats > div {
  border: 1px solid var(--line); border-radius: 10px; padding: 10px 8px;
  text-align: center; background: rgba(255,255,255,.75);
}
.hero-stats b { display: block; font-size: 21px; letter-spacing: -.4px; font-variant-numeric: tabular-nums; }
.hero-stats span { color: var(--muted); font-size: 12.5px; }

/* ---------------- 统计 ---------------- */
.stat { border: 1px solid var(--line); border-radius: var(--radius); padding: 16px; text-align: center; }
.stat b { display: block; font-size: 27px; line-height: 1.25; letter-spacing: -.6px; font-variant-numeric: tabular-nums; }
.stat span { color: var(--muted); font-size: 13px; }

/* ---------------- 表格 ---------------- */
table.list { width: 100%; border-collapse: collapse; font-size: 14px; }
table.list th {
  text-align: left; font-weight: 500; color: var(--muted); font-size: 12.5px;
  padding: 10px; border-bottom: 1px solid var(--line); white-space: nowrap;
}
table.list td { padding: 11px 10px; border-bottom: 1px solid var(--line); vertical-align: middle; }
table.list tbody tr:last-child td { border-bottom: 0; }
table.list tbody tr { transition: background .1s; }
table.list tbody tr:hover { background: var(--soft); }
table.list td.num, table.list th.num { text-align: center; color: var(--muted); font-variant-numeric: tabular-nums; }
table.list tr.top { background: linear-gradient(90deg, #fffbeb, transparent 60%); }
.rankno { font-size: 15px; }

/* ---------------- 标签 ---------------- */
.diff { font-size: 12.5px; padding: 2px 9px; border-radius: 20px; border: 1px solid var(--line); color: var(--muted); white-space: nowrap; }
.diff.d-入门 { color: #dc2626; border-color: #fecaca; background: #fef2f2; }
.diff.d-普及-, .diff.d-普及 { color: #b45309; border-color: #fed7aa; background: #fffbeb; }
.diff.d-提高 { color: #6d28d9; border-color: #ddd6fe; background: #f5f3ff; }
.tags { margin-top: 5px; }
.tag { font-size: 11.5px; color: var(--muted); border: 1px solid var(--line); border-radius: 5px; padding: 1px 6px; margin-right: 5px; background: var(--soft); }

.badge-admin { font-size: 11.5px; padding: 1px 7px; border-radius: 20px; background: #f5f3ff; color: #6d28d9; border: 1px solid #ddd6fe; }
.badge-owner {
  font-size: 11.5px; padding: 1px 8px; border-radius: 20px;
  background: linear-gradient(135deg, #fef3c7, #fde68a);
  color: #92400e; border: 1px solid #fcd34d; font-weight: 600;
  margin-left: 5px; white-space: nowrap;
}
.badge-admin { margin-left: 5px; white-space: nowrap; }
.uchip { display: inline-flex; align-items: center; gap: 6px; }
.uchip .badge-owner, .uchip .badge-admin { margin-left: 0; }
.badge-ban { font-size: 11.5px; padding: 1px 7px; border-radius: 20px; background: #fef2f2; color: #dc2626; border: 1px solid #fecaca; }
tr.row-owner td { background: linear-gradient(90deg, #fffbeb, transparent 70%); }
.notice {
  padding: 12px 16px; margin-bottom: 14px; font-size: 13.5px; color: #78350f;
  background: #fffbeb; border: 1px solid #fde68a; border-radius: 10px;
}

/* ---------------- 状态 ---------------- */
.v { font-weight: 600; font-size: 13.5px; }
.v-ok { color: var(--ok); }
.v-bad { color: var(--bad); }
.v-wait { color: var(--muted); }
.muted { color: var(--muted); }
.small { font-size: 13px; }

/* ---------------- 头像 ---------------- */
.avatar {
  display: inline-flex; align-items: center; justify-content: center;
  width: 30px; height: 30px; border-radius: 50%; flex: none;
  background: hsl(var(--h, 220) 72% 94%);
  color: hsl(var(--h, 220) 58% 40%);
  font-weight: 700; font-size: 14px; letter-spacing: -.3px;
  vertical-align: middle; text-transform: uppercase;
}
/* ---------------- 个人主页头部 ---------------- */
.cover {
  border: 1px solid var(--line); border-radius: 16px; overflow: hidden;
  margin-bottom: 18px; background: #fff;
}
.cover-bg {
  height: 96px;
  background:
    radial-gradient(520px 160px at 12% 0%, #dbeafe 0%, rgba(255,255,255,0) 70%),
    radial-gradient(520px 160px at 88% 0%, #ede9fe 0%, rgba(255,255,255,0) 70%),
    linear-gradient(120deg, #eff6ff, #f5f3ff 50%, #ecfdf5);
}
.cover-in {
  display: flex; align-items: flex-end; gap: 18px;
  padding: 0 26px 20px; margin-top: -46px;
}
.cover-avatar .avatar { border: 4px solid #fff; box-shadow: 0 6px 20px rgba(15,23,42,.14); }
.cover-text { flex: 1; min-width: 0; padding-bottom: 2px; }
.cover-text h1 { font-size: 25px; letter-spacing: -.5px; display: flex; align-items: center; gap: 8px; }
.cover-text .sub { margin-top: 2px; }
.cover .btn { margin-bottom: 4px; }

/* ---------------- 头像 ---------------- */
.avatar.img { object-fit: cover; border-radius: 50%; display: inline-block; }
.avatar.emoji { line-height: 1; }
.uchip { display: inline-flex; align-items: center; gap: 7px; white-space: nowrap; }
.uchip .avatar { vertical-align: middle; }

/* ---------------- 头像选择器 ---------------- */
.avatar-picker { display: flex; gap: 22px; align-items: flex-start; margin-top: 4px; }
.ap-current { flex: none; }
.ap-current .avatar { border: 3px solid #fff; box-shadow: 0 6px 18px rgba(15,23,42,.14); }
.ap-body { flex: 1; min-width: 0; }
.emoji-grid { display: flex; flex-wrap: wrap; gap: 8px; }
.emoji-opt {
  width: 44px; height: 44px; border-radius: 12px; cursor: pointer;
  border: 1px solid var(--line); background: var(--soft);
  font-size: 22px; line-height: 1; padding: 0;
  transition: transform .1s, border-color .12s, background .12s;
}
.emoji-opt:hover { border-color: var(--accent); background: var(--accent-soft); transform: translateY(-2px); }
.emoji-opt:active { transform: translateY(0) scale(.96); }
.ap-actions { display: flex; align-items: center; gap: 10px; margin-top: 14px; flex-wrap: wrap; }
.ap-actions label.btn { cursor: pointer; }

.row-form { display: flex; gap: 10px; }
.row-form input { flex: 1; }
.ok-note { color: var(--ok); }

/* ---------------- 按钮 ---------------- */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 6px;
  font: inherit; font-size: 14px; padding: 7px 16px;
  border-radius: 8px; border: 1px solid var(--line); cursor: pointer;
  background: #fff; color: var(--fg2);
  transition: background .12s, border-color .12s, color .12s, opacity .12s, transform .06s;
}
.btn:hover { border-color: #c3cad9; color: var(--fg); }
.btn:active { transform: translateY(1px); }
.btn.primary { background: var(--accent); border-color: var(--accent); color: #fff; }
.btn.primary:hover { background: var(--accent-d); border-color: var(--accent-d); color: #fff; }
.btn.lg { padding: 10px 22px; font-size: 15px; border-radius: 9px; }
.btn.sm { padding: 4px 12px; font-size: 13px; border-radius: 7px; }
.btn.danger { border-color: #fecaca; color: var(--bad); }
.btn.danger:hover { background: #fef2f2; border-color: #fca5a5; }
.btn:disabled { opacity: .5; cursor: default; }
.btn.link { border: 0; background: none; color: var(--muted); padding: 2px 6px; font-size: 13px; }
.btn.link:hover { color: var(--bad); text-decoration: underline; }
.del { margin-left: 6px; }

/* ---------------- 表单 ---------------- */
input[type=text], input[type=password], textarea, select {
  font: inherit; width: 100%; padding: 9px 12px;
  border: 1px solid var(--line); border-radius: 8px; outline: none;
  background: #fff; color: var(--fg); transition: border-color .12s, box-shadow .12s;
}
input:focus, textarea:focus, select:focus {
  border-color: var(--accent); box-shadow: 0 0 0 3px rgba(37,99,235,.1);
}
textarea { resize: vertical; }
label.field { display: block; margin-bottom: 15px; }
label.field > span { display: block; font-size: 13px; color: var(--muted); margin-bottom: 6px; }
.md-tip { font-size: 12.5px; color: var(--muted); margin-top: 8px; line-height: 2; }
.md-tip code { background: var(--soft); border: 1px solid var(--line); border-radius: 5px; padding: 1px 6px; font-size: 11.5px; }

.authbox { max-width: 390px; margin: 46px auto; }
.authbox h1 { margin-bottom: 18px; }

/* ---------------- 标签页 ---------------- */
.tabs { display: flex; gap: 6px; margin-bottom: 18px; border-bottom: 1px solid var(--line); flex-wrap: wrap; }
.tabs a { padding: 9px 15px; font-size: 14px; color: var(--muted); border-bottom: 2px solid transparent; margin-bottom: -1px; }
.tabs a:hover { color: var(--fg); }
.tabs a.on { color: var(--accent); border-bottom-color: var(--accent); font-weight: 600; }

/* ---------------- 题面 ---------------- */
.stmt { border: 1px solid var(--line); border-radius: var(--radius); padding: 24px 26px; margin-bottom: 18px; }
.stmt-head { display: flex; align-items: center; gap: 12px; margin-bottom: 6px; }
.stmt .meta { font-size: 13px; color: var(--muted); margin-bottom: 4px; }
.stmt h3 { font-size: 14px; margin: 24px 0 8px; color: var(--fg2); }
.body-text { white-space: pre-wrap; color: var(--fg2); }
.samples { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin-bottom: 12px; }
.samples .lbl { font-size: 12px; color: var(--muted); margin-bottom: 4px; }
pre.box {
  margin: 0; font-family: var(--mono); font-size: 13px; line-height: 1.6;
  background: var(--soft); border: 1px solid var(--line); border-radius: 8px;
  padding: 10px 12px; overflow-x: auto; white-space: pre;
}

/* ---------------- 编辑器 ---------------- */
.editor { border: 1px solid var(--line); border-radius: var(--radius); overflow: hidden; margin-bottom: 18px; }
.editor .head {
  display: flex; align-items: center; gap: 10px; padding: 9px 14px;
  background: var(--soft); border-bottom: 1px solid var(--line); font-size: 13px; color: var(--muted);
}
.editor textarea {
  border: 0; border-radius: 0; height: 310px; resize: vertical;
  font-family: var(--mono); font-size: 13.5px; line-height: 1.68; tab-size: 4;
  background: #fcfdff;
}
.editor textarea:focus { box-shadow: none; background: #fff; }
.editor .foot {
  display: flex; align-items: center; gap: 14px; padding: 12px 14px;
  border-top: 1px solid var(--line); background: var(--soft);
}

/* ---------------- 结果 ---------------- */
.rrow { display: flex; align-items: center; gap: 14px; padding: 9px 12px; border-bottom: 1px solid var(--line); font-size: 14px; }
.rrow:first-of-type { border-top: 1px solid var(--line); }
.rrow .name { color: var(--muted); font-variant-numeric: tabular-nums; }
.rrow .time { margin-left: auto; color: var(--muted); font-size: 13px; font-variant-numeric: tabular-nums; }

pre.code, pre.md-code {
  margin: 0; font-family: var(--mono); font-size: 13px; line-height: 1.65;
  background: #0f172a; color: #e2e8f0;
  border-radius: 10px; padding: 15px 17px; overflow-x: auto; white-space: pre;
  tab-size: 4;
}
pre.err {
  margin: 0; font-family: var(--mono); font-size: 12.5px; line-height: 1.55;
  background: #fef2f2; border: 1px solid #fecaca; border-radius: 10px;
  padding: 12px 14px; overflow-x: auto; white-space: pre-wrap; word-break: break-word; color: #7f1d1d;
}
/* 语法高亮 */
.tk-k { color: #c792ea; }
.tk-s { color: #a5e075; }
.tk-c { color: #64748b; font-style: italic; }
.tk-p { color: #7dd3fc; }
.tk-n { color: #fbbf24; }

details.diff { margin: 4px 0 10px 12px; font-size: 13px; }
details.diff summary { cursor: pointer; color: var(--muted); }
details.diff summary:hover { color: var(--accent); }
details.diff .dgrid { display: grid; grid-template-columns: 1fr 1fr 1fr; gap: 10px; margin-top: 8px; }
details.diff .lbl { font-size: 12px; color: var(--muted); margin-bottom: 3px; }
details.diff pre {
  margin: 0; font-family: var(--mono); font-size: 12.5px; line-height: 1.5;
  background: var(--soft); border: 1px solid var(--line); border-radius: 7px;
  padding: 8px 10px; overflow: auto; max-height: 200px; white-space: pre-wrap; word-break: break-word;
}

/* ---------------- 列表项 / 帖子 ---------------- */
.item { padding: 15px 0; border-bottom: 1px solid var(--line); }
.item:last-child { border-bottom: 0; }
.item .t { font-size: 15.5px; font-weight: 500; }
.item .meta { font-size: 12.5px; color: var(--muted); margin-top: 3px; }
.item .excerpt { color: var(--fg2); font-size: 13.5px; margin-top: 6px; white-space: pre-wrap; }

.post { border: 1px solid var(--line); border-radius: var(--radius); padding: 22px 24px; margin-bottom: 16px; }
.post .who { font-size: 13px; color: var(--muted); margin-bottom: 14px; display: flex; align-items: center; gap: 7px; }
.reply { border: 1px solid var(--line); border-radius: var(--radius); padding: 15px 17px; margin-bottom: 12px; }
.reply .who { font-size: 12.5px; color: var(--muted); margin-bottom: 9px; display: flex; align-items: center; gap: 7px; }
.reply .who .del { margin-left: auto; }

/* ---------------- Markdown 正文 ---------------- */
.md { color: var(--fg2); font-size: 14.5px; }
.md > *:first-child { margin-top: 0; }
.md > *:last-child { margin-bottom: 0; }
.md p { margin: 0 0 12px; }
.md h3, .md h4, .md h5, .md h6 { margin: 20px 0 9px; color: var(--fg); font-size: 16px; }
.md h4 { font-size: 15px; }
.md h5, .md h6 { font-size: 14.5px; }
.md ul, .md ol { margin: 0 0 12px; padding-left: 24px; }
.md li { margin: 3px 0; }
.md blockquote {
  margin: 0 0 12px; padding: 6px 14px; border-left: 3px solid #c7d2fe;
  background: #f8faff; color: var(--muted); border-radius: 0 8px 8px 0;
}
.md hr { border: 0; border-top: 1px solid var(--line); margin: 18px 0; }
.md code {
  font-family: var(--mono); font-size: 12.8px; background: #f1f5f9;
  border: 1px solid var(--line); border-radius: 5px; padding: 1px 5px; color: #be185d;
}
.md pre.code { margin: 0 0 12px; }
.md pre.code code { background: none; border: 0; padding: 0; color: inherit; font-size: inherit; }
.md a { color: var(--accent); text-decoration: underline; text-underline-offset: 2px; }
.md img { max-width: 100%; border-radius: 8px; }
.md strong { color: var(--fg); }

/* ---------------- 空状态 / 提示 ---------------- */
.empty { padding: 34px 0; text-align: center; color: var(--muted); font-size: 14px; }
.toast {
  position: fixed; left: 50%; bottom: 36px; transform: translateX(-50%);
  background: #0f172a; color: #fff; padding: 10px 22px; border-radius: 10px;
  font-size: 14px; z-index: 200; box-shadow: 0 8px 26px rgba(15,23,42,.22);
}

.chip {
  display: inline-block; font-size: 13px; padding: 4px 12px; margin: 0 6px 6px 0;
  border: 1px solid var(--line); border-radius: 20px; color: var(--fg2); background: var(--soft);
  transition: border-color .12s, color .12s;
}
.chip:hover { border-color: var(--accent); color: var(--accent); background: var(--accent-soft); }

/* ---------------- 细节打磨 ---------------- */

/* 滚动条 */
* { scrollbar-width: thin; scrollbar-color: #cbd5e1 transparent; }
::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: #cbd5e1; border-radius: 10px; border: 3px solid #fff; }
::-webkit-scrollbar-thumb:hover { background: #94a3b8; }

/* 主按钮更有质感 */
.btn.primary {
  background: linear-gradient(180deg, #3b82f6, #2563eb);
  border-color: #2563eb;
  box-shadow: 0 1px 2px rgba(37,99,235,.25), inset 0 1px 0 rgba(255,255,255,.18);
}
.btn.primary:hover {
  background: linear-gradient(180deg, #2563eb, #1d4ed8);
  border-color: #1d4ed8;
}
.card { box-shadow: 0 1px 2px rgba(15,23,42,.025); }
.card:hover { box-shadow: 0 6px 24px rgba(15,23,42,.06); }
.stat { background: linear-gradient(180deg, #fff, #fcfdff); }
.stat:hover { border-color: #d7dced; }

/* 表格更清爽 */
table.list th { background: var(--soft); }
table.list th:first-child { border-top-left-radius: 8px; }
table.list th:last-child { border-top-right-radius: 8px; }

/* 空状态 */
.empty::before {
  content: ''; display: block; width: 34px; height: 34px; margin: 0 auto 12px;
  border-radius: 12px; background: linear-gradient(135deg, #e2e8f0, #eef2ff);
}

/* 焦点可见性 */
a:focus-visible, button:focus-visible, input:focus-visible,
textarea:focus-visible, select:focus-visible {
  outline: 2px solid var(--accent); outline-offset: 2px;
}

/* 顶栏用户区 */
.userbox .me { padding: 4px 10px 4px 4px; border-radius: 20px; transition: background .12s; }
.userbox .me:hover { background: var(--soft); color: var(--fg); }

/* 卡片内标题 */
.card > h2:first-child { margin-top: 0; }

@media (prefers-reduced-motion: reduce) {
  * { transition: none !important; }
}

/* ---------------- 比赛 ---------------- */
.contest-card { transition: border-color .15s, box-shadow .15s, transform .1s; }
.contest-card:hover { transform: translateY(-1px); }
.contest-top { display: flex; align-items: center; gap: 12px; margin-bottom: 4px; }
.contest-title { font-size: 17px; font-weight: 600; }
.contest-title:hover { color: var(--accent); }

.pill {
  font-size: 12px; padding: 2px 10px; border-radius: 20px;
  border: 1px solid var(--line); color: var(--muted); white-space: nowrap;
}
.pill-ok { color: var(--ok); border-color: #a7f3d0; background: #ecfdf5; }
.pill-wait { color: var(--warn); border-color: #fed7aa; background: #fffbeb; }
.pill-muted { color: var(--muted); background: var(--soft); }

.contest-head {
  display: flex; align-items: flex-start; gap: 20px;
  justify-content: space-between; margin-bottom: 18px; flex-wrap: wrap;
}
.contest-head h1 { font-size: 25px; margin-bottom: 4px; }
.contest-clock {
  font-family: var(--mono); font-size: 15px; color: var(--fg2);
  border: 1px solid var(--line); border-radius: 10px; padding: 10px 18px;
  background: linear-gradient(180deg, #fff, var(--soft));
}
.contest-clock b { color: var(--accent); font-size: 17px; }

/* ---------------- 管理：题目上传 ---------------- */
.form-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 0 16px; }

.pair {
  display: flex; gap: 14px; align-items: flex-start;
  padding: 14px 0; border-bottom: 1px solid var(--line);
}
.pair:last-child { border-bottom: 0; }
.pair-no { width: 62px; flex: none; color: var(--muted); font-size: 13px; padding-top: 26px; }
.pair-body { flex: 1; display: grid; grid-template-columns: 1fr 1fr; gap: 14px; min-width: 0; }
.pair-body textarea { font-family: var(--mono); font-size: 13px; }
.pair > .btn { margin-top: 26px; flex: none; }

.pick-list {
  border: 1px solid var(--line); border-radius: 10px;
  max-height: 320px; overflow-y: auto; padding: 6px;
}
.pick {
  display: flex; align-items: center; gap: 10px;
  padding: 8px 12px; border-radius: 8px; cursor: pointer; font-size: 14px;
}
.pick:hover { background: var(--soft); }
.pick input { width: auto; }
.pick .muted { margin-left: auto; }

/* ---------------- 题目页双栏布局 ---------------- */
.p-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 208px;
  gap: 22px;
  align-items: start;
}
.p-main { min-width: 0; }
.p-side { position: sticky; top: 76px; display: flex; flex-direction: column; gap: 12px; }
.side-card {
  display: block; border: 1px solid var(--line); border-radius: 12px;
  padding: 14px 16px; background: #fff;
  transition: border-color .15s, box-shadow .15s, transform .1s;
}
.side-card:hover { border-color: #c7d2fe; box-shadow: 0 6px 20px rgba(37,99,235,.08); transform: translateY(-1px); }
.sc-top { display: flex; align-items: baseline; justify-content: space-between; }
.sc-title { font-weight: 600; font-size: 15px; }
.sc-num { font-size: 20px; font-weight: 700; color: var(--accent); font-variant-numeric: tabular-nums; }
.sc-hint { font-size: 12.5px; color: var(--muted); margin-top: 4px; }
.sc-more { font-size: 12.5px; color: var(--accent); margin-top: 8px; }

/* ---------------- 搜索栏 ---------------- */
.searchbar { display: flex; gap: 10px; margin-bottom: 14px; }
.searchbar input { flex: 1; }
.tag.idtag { font-family: var(--mono); color: var(--accent); border-color: #c7d2fe; background: var(--accent-soft); }

/* ---------------- LaTeX 公式 ---------------- */
.tex-block { margin: 14px 0; overflow-x: auto; overflow-y: hidden; padding: 2px 0; }
.tex-block .katex-display { margin: 0; }
.katex { font-size: 1.05em; }
.tex-plain {
  font-family: var(--mono); font-size: 13.5px;
  background: #f8fafc; border: 1px solid var(--line); border-radius: 5px; padding: 1px 5px;
}
/* 公式太长时允许横向滚动，不要撑破卡片 */
.content.md .katex-display { overflow-x: auto; overflow-y: hidden; }

/* ---------------- 通知 / 私信 / 犇犇 ---------------- */
.icon-btn {
  position: relative; width: 34px; height: 34px; border-radius: 9px;
  display: inline-flex; align-items: center; justify-content: center;
  font-size: 16px; color: var(--text); border: 1px solid transparent;
}
.icon-btn:hover { background: #f1f5f9; border-color: var(--line); }
.icon-btn .dot {
  position: absolute; top: -4px; right: -5px; min-width: 17px; height: 17px; padding: 0 4px;
  border-radius: 9px; background: #ef4444; color: #fff; font-size: 10.5px; font-style: normal;
  line-height: 17px; text-align: center; font-weight: 600;
}
.notif {
  display: flex; gap: 12px; align-items: flex-start; padding: 12px 4px;
  border-bottom: 1px solid var(--line);
}
.notif:last-child { border-bottom: 0; }
.notif.unread { background: linear-gradient(90deg, #eff6ff, transparent 60%); }
.nicon { width: 30px; height: 30px; border-radius: 9px; background: #f1f5f9; flex: none;
  display: flex; align-items: center; justify-content: center; font-size: 14px; }
.nbody { flex: 1; min-width: 0; display: flex; flex-direction: column; gap: 3px; }
.ntext { font-size: 14px; }
.nctx { font-size: 12.5px; color: var(--muted); overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.ntime { flex: none; }

.convo {
  display: flex; gap: 14px; align-items: center; padding: 13px 10px;
  border-bottom: 1px solid var(--line); border-radius: 10px;
}
.convo:last-child { border-bottom: 0; }
.convo:hover { background: #f8fafc; }
.cbody { flex: 1; min-width: 0; display: flex; flex-direction: column; gap: 3px; }
.crow { display: flex; justify-content: space-between; align-items: baseline; gap: 10px; }
.crow b { font-size: 15px; }
.cpreview { font-size: 13px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.convo .dot {
  min-width: 19px; height: 19px; border-radius: 10px; background: #ef4444; color: #fff;
  font-size: 11px; font-style: normal; line-height: 19px; text-align: center; font-weight: 600; padding: 0 5px;
}

.chat { display: flex; flex-direction: column; gap: 10px; max-height: 60vh; overflow-y: auto; padding: 4px 2px; }
.bubble { max-width: 74%; padding: 9px 13px; border-radius: 14px; }
.bubble.theirs { align-self: flex-start; background: #f1f5f9; border-bottom-left-radius: 4px; }
.bubble.mine { align-self: flex-end; background: var(--accent-soft); border: 1px solid #c7d2fe; border-bottom-right-radius: 4px; }
.btext { font-size: 14px; }
.bubble.mine .btime { text-align: right; }

.compose { margin-top: 16px; }
.compose textarea { width: 100%; }
.compose-foot { display: flex; justify-content: space-between; align-items: center; margin-top: 10px; }

.bb { padding: 16px 2px; border-bottom: 1px solid var(--line); }
.bb:last-child { border-bottom: 0; }
.bb-head { display: flex; align-items: center; gap: 10px; margin-bottom: 8px; }
.bb-body { font-size: 14.5px; margin-bottom: 10px; }
.bb-foot { display: flex; gap: 14px; align-items: center; }
.bblike.on { color: #e11d48; }

.ctabs { display: flex; gap: 6px; margin-bottom: 14px; flex-wrap: wrap; }
.ctab {
  padding: 7px 14px; border-radius: 9px; border: 1px solid var(--line); background: #fff;
  font-size: 14px; display: inline-flex; align-items: center; gap: 6px;
}
.ctab:hover { border-color: #c7d2fe; }
.ctab.on { background: var(--accent); color: #fff; border-color: var(--accent); }
.ctab i { font-style: normal; font-size: 12px; opacity: .7; }
.cat-badge {
  font-size: 11.5px; padding: 1px 7px; border-radius: 20px; margin-left: 6px;
  background: #f1f5f9; color: var(--muted); border: 1px solid var(--line); font-weight: 400;
}
.cat-problem { background: #eff6ff; color: #1d4ed8; border-color: #bfdbfe; }
.cat-admin { background: #fef2f2; color: #b91c1c; border-color: #fecaca; }
.cat-chat { background: #f0fdf4; color: #15803d; border-color: #bbf7d0; }

.userrow {
  display: flex; align-items: center; gap: 14px;
  padding: 13px 10px; border-bottom: 1px solid var(--line);
  border-radius: 10px; transition: background .12s;
}
.userrow:hover { background: #f8fafc; }
.userrow:last-child { border-bottom: 0; }
.uavatar { flex: none; line-height: 0; border-radius: 50%; }
.ubody { flex: 1; min-width: 0; display: flex; flex-direction: column; gap: 3px; }
.uname { font-weight: 600; font-size: 15px; }
.uname:hover { color: var(--accent); }
.ubio {
  font-size: 13px; color: var(--muted);
  overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
}
.utime { flex: none; }

.cover-actions { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; }
.stat { text-decoration: none; color: inherit; }
a.stat:hover { border-color: #c7d2fe; }
.ann-item .t { display: flex; align-items: center; gap: 6px; }

/* ---------------- 窄屏 ---------------- */
@media (max-width: 880px) {
  .topbar { gap: 12px; padding: 0 14px; overflow-x: auto; }
  .nav { gap: 0; font-size: 14px; }
  .nav a { padding: 6px 9px; }
  .container { padding: 20px 14px 70px; }
  .hero { grid-template-columns: 1fr; padding: 24px 20px; }
  .hero h1 { font-size: 27px; }
  .grid2, .grid4, .samples, .two-col { grid-template-columns: 1fr; }
  details.diff .dgrid { grid-template-columns: 1fr; }
  .cover-bg { height: 74px; }
  .cover-in { flex-wrap: wrap; padding: 0 18px 18px; margin-top: -40px; gap: 14px; }
  .cover-text h1 { font-size: 21px; }
  .avatar-picker { flex-direction: column; gap: 16px; }
  .row-form { flex-direction: column; }
  .form-grid { grid-template-columns: 1fr; }
  .pair { flex-wrap: wrap; }
  .pair-no { width: 100%; padding-top: 0; }
  .pair-body { grid-template-columns: 1fr; }
  .pair > .btn { margin-top: 0; }
  .p-layout { grid-template-columns: 1fr; }
  .p-side { position: static; flex-direction: row; }
  .side-card { flex: 1; }
}