:root {
  --bg: #f7f8fa;
  --panel: #ffffff;
  --panel-2: #f2f3f5;
  --border: #e3e5e8;
  --text: #1f2328;
  --muted: #6b7280;
  --accent: #2563eb;
  --accent-soft: #e8efff;
  --ok: #15803d;
  --ok-soft: #e7f6ec;
  --bad: #dc2626;
  --bad-soft: #fdecec;
  --warn: #b45309;
  --easy: #16a34a;
  --medium: #d97706;
  --hard: #dc2626;
  --hl: #fff3b0;
  --hl-row: #fde8e8;
  --code-bg: #f6f8fa;
  --mono: ui-monospace, SFMono-Regular, "JetBrains Mono", Menlo, Consolas, monospace;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #16181d;
    --panel: #1e2128;
    --panel-2: #262a33;
    --border: #343946;
    --text: #e6e8ec;
    --muted: #9aa3b2;
    --accent: #6ea0ff;
    --accent-soft: #233154;
    --ok: #4ade80;
    --ok-soft: #173325;
    --bad: #f87171;
    --bad-soft: #3a1d20;
    --warn: #fbbf24;
    --hl: #5a4a10;
    --hl-row: #47242a;
    --code-bg: #262a33;
    color-scheme: dark;
  }
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body { background: var(--bg); color: var(--text); font: 14px/1.55 var(--sans); }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
code, pre, kbd { font-family: var(--mono); }
pre { margin: 0; white-space: pre-wrap; word-break: break-word; }
kbd { font-size: 11px; padding: 0 4px; border: 1px solid var(--border); border-radius: 4px; color: var(--muted); }
.muted { color: var(--muted); }
.small { font-size: 12px; }
.spacer { flex: 1; }
[hidden] { display: none !important; }

/* top bar */
.topbar { height: 48px; display: flex; align-items: center; gap: 14px; padding: 0 16px;
  background: var(--panel); border-bottom: 1px solid var(--border); position: sticky; top: 0; z-index: 20; }
.brand { font-weight: 700; font-size: 17px; color: var(--text); letter-spacing: .2px; }
.tagline { color: var(--muted); font-size: 12px; }
.navlink { color: var(--text); }

/* buttons */
.btn { font: inherit; border: 1px solid var(--border); background: var(--panel); color: var(--text);
  padding: 5px 12px; border-radius: 6px; cursor: pointer; display: inline-flex; align-items: center; gap: 6px; }
.btn:hover { background: var(--panel-2); text-decoration: none; }
.btn.primary { background: var(--accent); border-color: var(--accent); color: #fff; font-weight: 600; }
.btn.primary kbd { color: #dbe6ff; border-color: #ffffff55; }
.btn.primary:hover { filter: brightness(1.08); }
.btn.ghost { background: transparent; }
.btn.tiny { padding: 1px 8px; font-size: 12px; }
.btn.danger { background: var(--bad); border-color: var(--bad); color: #fff; }
.btn:disabled, .btn.busy { opacity: .6; cursor: progress; }

/* shell + cheat drawer */
.shell { display: flex; min-height: calc(100vh - 48px); }
.main { flex: 1; min-width: 0; }
.drawer { width: 0; overflow: hidden; background: var(--panel); border-left: 1px solid var(--border);
  position: sticky; top: 48px; height: calc(100vh - 48px); display: flex; flex-direction: column; }
body.cheat-open .drawer { width: min(660px, 46vw); }
.drawer-head { display: flex; gap: 8px; padding: 10px; border-bottom: 1px solid var(--border); }
.drawer-head input { flex: 1; }
.drawer-body { overflow: auto; padding: 10px 12px 40px; container-type: inline-size; }
input[type=search], input[type=text], select { font: inherit; padding: 5px 9px; border: 1px solid var(--border);
  border-radius: 6px; background: var(--panel); color: var(--text); }

.cheat-section h4 { margin: 18px 0 6px; font-size: 13px; color: var(--muted); border-bottom: 1px solid var(--border); padding-bottom: 4px; }
.concept { padding: 8px 0; border-bottom: 1px dashed var(--border); }
.concept-name { font-weight: 600; margin-bottom: 4px; }
.concept-note { color: var(--warn); margin-bottom: 4px; }
.concept-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 6px; }
@container (min-width: 600px) { .concept-grid { grid-template-columns: repeat(4, minmax(0, 1fr)); } }
.cell { background: var(--panel-2); border-radius: 6px; padding: 5px 7px; min-width: 0; }
.cell-lib { font-size: 11px; color: var(--muted); text-transform: uppercase; letter-spacing: .4px; }
.cell-api code { font-size: 12px; word-break: break-word; }
.cell-ex { font-size: 11.5px; color: var(--muted); margin-top: 2px; }
.cell-note { color: var(--warn); }

/* index */
.page { max-width: 1100px; margin: 0 auto; padding: 18px 20px 60px; }
.stats { display: grid; grid-template-columns: repeat(4, 1fr); gap: 10px; margin-bottom: 14px; }
.stat { background: var(--panel); border: 1px solid var(--border); border-radius: 10px; padding: 10px 14px;
  display: flex; flex-direction: column; }
.stat-label { color: var(--muted); font-size: 12px; }
.stat-num { font-size: 20px; font-weight: 700; }
.filters { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; margin-bottom: 14px;
  background: var(--panel); border: 1px solid var(--border); border-radius: 10px; padding: 10px; }
.filters .search { width: 200px; }
.filters .count { margin-left: auto; }
.chips { border: 0; margin: 0; padding: 0; display: flex; gap: 6px; }
.chip { border: 1px solid var(--border); border-radius: 999px; padding: 2px 10px; cursor: pointer; user-select: none; }
.chip input { display: none; }
.chip:has(input:checked) { background: var(--accent-soft); border-color: var(--accent); }
.dropdown { position: relative; }
.dropdown summary { list-style: none; cursor: pointer; border: 1px solid var(--border); border-radius: 6px; padding: 5px 10px; }
.dropdown summary::-webkit-details-marker { display: none; }
.dropdown-body { position: absolute; z-index: 10; top: 36px; left: 0; background: var(--panel); border: 1px solid var(--border);
  border-radius: 8px; padding: 8px 12px; width: 320px; max-height: 360px; overflow: auto; box-shadow: 0 8px 24px #0002; }
.dropdown-body label { display: block; padding: 2px 0; white-space: nowrap; }
.group { background: var(--panel); border: 1px solid var(--border); border-radius: 10px; margin-bottom: 10px; overflow: hidden; }
.group > summary { cursor: pointer; padding: 9px 14px; font-weight: 600; background: var(--panel-2); }
.topic-id { font-family: var(--mono); color: var(--muted); font-weight: 500; margin-right: 4px; }
.plist { width: 100%; border-collapse: collapse; }
.plist td { padding: 7px 14px; border-top: 1px solid var(--border); }
.plist tr:hover td { background: var(--panel-2); }
.plist .title a { color: var(--text); font-weight: 500; }
.pid { color: var(--muted); font-size: 12px; font-family: var(--mono); margin-left: 6px; }
.plist .diff { width: 70px; }
.plist .dots { width: 110px; text-align: right; white-space: nowrap; }
.dot { display: inline-block; width: 11px; height: 11px; border-radius: 50%; margin-left: 6px; vertical-align: middle; }
.dot-passed { background: var(--ok); }
.dot-todo { border: 2px solid var(--muted); opacity: .6; }
.dot-na { background: var(--border); width: 11px; height: 3px; border-radius: 2px; }
.badge { display: inline-block; font-size: 12px; padding: 0 8px; border-radius: 999px; background: var(--panel-2); }
.badge.diff-easy { color: var(--easy); } .badge.diff-medium { color: var(--medium); } .badge.diff-hard { color: var(--hard); }
.chip.diff-easy { color: var(--easy); } .chip.diff-medium { color: var(--medium); } .chip.diff-hard { color: var(--hard); }
.tag { font-size: 12px; color: var(--muted); background: var(--panel-2); padding: 0 6px; border-radius: 4px; }
.warn { background: var(--bad-soft); padding: 8px 12px; border-radius: 8px; margin-bottom: 10px; }
.empty { color: var(--muted); padding: 40px; text-align: center; }

/* problem page */
body.problem-page .main { height: calc(100vh - 48px); overflow: hidden; }
.workspace { display: flex; height: 100%; }
.left { flex: 0 0 44%; overflow: auto; padding: 14px 20px 60px; background: var(--panel); min-width: 0; }
.right { flex: 1; min-width: 0; display: flex; flex-direction: column; overflow: auto; padding: 10px 14px 40px; }
.divider { width: 6px; cursor: col-resize; background: var(--border); flex: 0 0 6px; }
.divider:hover, body.dragging .divider { background: var(--accent); }
body.dragging { user-select: none; cursor: col-resize; }
.pnav { display: flex; gap: 12px; font-size: 13px; }
.ptitle { font-size: 20px; margin: 8px 0 6px; }
.meta { display: flex; gap: 6px; flex-wrap: wrap; align-items: center; margin-bottom: 10px; }
.section-title { font-size: 14px; margin: 22px 0 8px; display: flex; gap: 8px; align-items: center; flex-wrap: wrap; }
.markdown p { margin: 6px 0; }
.markdown ul { padding-left: 20px; margin: 6px 0; }
.markdown code { background: var(--code-bg); padding: 1px 5px; border-radius: 4px; font-size: 12.5px; }
.markdown pre code { display: block; padding: 8px; }
.markdown table { border-collapse: collapse; margin: 8px 0; }
.markdown th, .markdown td { border: 1px solid var(--border); padding: 3px 8px; }
.input-table { margin-bottom: 14px; }
.input-head { display: flex; align-items: center; gap: 8px; margin-bottom: 4px; }
.tname { font-weight: 700; }
.filetext { background: var(--code-bg); padding: 8px; border-radius: 6px; font-size: 12px; max-height: 300px; overflow: auto; }

.tablewrap { overflow: auto; max-height: 420px; border: 1px solid var(--border); border-radius: 6px; }
table.data { border-collapse: collapse; font-size: 12.5px; width: max-content; min-width: 100%; }
table.data th, table.data td { padding: 3px 9px; border-bottom: 1px solid var(--border); text-align: left;
  white-space: nowrap; font-family: var(--mono); }
table.data th { position: sticky; top: 0; background: var(--panel-2); font-family: var(--sans); z-index: 1; }
table.data th .col { display: block; font-weight: 600; }
table.data th .dtype { display: block; font-weight: 400; color: var(--muted); font-size: 11px; font-family: var(--mono); }
table.data td.null { color: var(--muted); font-style: italic; }
table.data .rownum { color: var(--muted); text-align: right; width: 1%; }
table.data.compact { width: auto; }
tr.hl-row td { background: var(--hl-row); }
td.hl-cell { background: var(--hl) !important; font-weight: 600; }

.tabbar { display: flex; gap: 2px; border-bottom: 1px solid var(--border); }
.tab { font: inherit; border: 0; background: transparent; color: var(--muted); padding: 8px 14px; cursor: pointer;
  border-bottom: 2px solid transparent; margin-bottom: -1px; }
.tab:hover { color: var(--text); }
.tab.active { color: var(--text); border-bottom-color: var(--accent); font-weight: 600; }
.tab.disabled { opacity: .38; cursor: not-allowed; }
.tab-check { color: var(--ok); margin-left: 4px; font-weight: 700; }
.na-box { margin: 8px 0; padding: 8px 10px; background: var(--panel-2); border-radius: 6px; color: var(--muted); }
.editors { margin-top: 8px; }
.editor-host { border: 1px solid var(--border); border-radius: 8px; overflow: hidden; background: var(--panel); }
.editor-host .cm-editor { height: 340px; font-size: 13.5px; }
.editor-host .cm-scroller { font-family: var(--mono); }
.actions { display: flex; gap: 8px; align-items: center; margin: 10px 0; flex-wrap: wrap; }

.results { background: var(--panel); border: 1px solid var(--border); border-radius: 8px; padding: 10px 12px; }
.summary { display: flex; gap: 10px; align-items: baseline; margin-bottom: 8px; font-weight: 600; }
.pass-banner { color: #fff; background: var(--ok); padding: 3px 14px; border-radius: 6px; font-size: 16px; }
.fail-banner { color: var(--bad); }
.case-tabs { display: flex; gap: 6px; flex-wrap: wrap; margin-bottom: 8px; }
.case-tab { font: inherit; font-size: 13px; border: 1px solid var(--border); background: var(--panel-2); color: var(--text);
  border-radius: 6px; padding: 2px 10px; cursor: pointer; }
.case-tab.ok .mark { color: var(--ok); font-weight: 700; }
.case-tab.bad .mark { color: var(--bad); font-weight: 700; }
.case-tab.active { border-color: var(--accent); background: var(--accent-soft); }
.error-box { background: var(--bad-soft); border: 1px solid var(--bad); border-radius: 6px; padding: 8px 10px; margin-bottom: 8px; }
.error-box pre { font-size: 12.5px; }
.error-title { font-weight: 700; color: var(--bad); margin-bottom: 4px; }
.outbox { background: var(--code-bg); border-radius: 6px; padding: 6px 10px; margin-bottom: 8px; max-height: 240px; overflow: auto; }
.outbox-title { font-size: 11px; color: var(--muted); }
.outbox pre { font-size: 12px; }
.diff { margin-bottom: 10px; }
.diff-msg { color: var(--bad); font-weight: 600; margin-bottom: 6px; }
.collist { margin: 4px 0 8px; padding-left: 18px; }
.collist .missing { color: var(--bad); } .collist .extra { color: var(--warn); }
.diffblock { margin: 8px 0; }
.diffblock-title { font-size: 12.5px; font-weight: 600; margin-bottom: 3px; }
.diffblock.missing .diffblock-title { color: var(--bad); }
.diffblock.extra .diffblock-title { color: var(--warn); }
.side-by-side { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
.sbs-col { min-width: 0; }
.sbs-title { font-size: 12px; font-weight: 600; color: var(--muted); margin-bottom: 3px; }
.running { padding: 12px; }

/* answers */
.answers-panel { height: 100%; overflow: auto; padding: 14px 20px 60px; }
.answers-head { display: flex; align-items: center; gap: 10px; }
.answers-head h2 { font-size: 18px; margin: 0; }
.answers-grid { display: grid; gap: 12px; margin-top: 12px; grid-template-columns: 1fr; }
@media (min-width: 1200px) {
  .answers-grid.n4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }
  .answers-grid.n3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .answers-grid.n2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}
.answer { background: var(--panel); border: 1px solid var(--border); border-radius: 8px; padding: 8px 10px; min-width: 0; }
.answer-title { font-weight: 700; margin-bottom: 6px; }
.notes { background: var(--panel); border: 1px solid var(--border); border-radius: 8px; padding: 6px 16px 12px; margin-top: 12px; }
.notes h3 { font-size: 15px; }

/* modal */
.modal { position: fixed; inset: 0; background: #0007; z-index: 50; display: flex; align-items: center; justify-content: center; }
.modal-card { background: var(--panel); border-radius: 10px; width: min(860px, 92vw); max-height: 86vh; overflow: auto; padding: 12px 16px; }
.modal-head { display: flex; align-items: center; margin-bottom: 8px; }

/* pygments (class prefix .hl) – theme-aware */
.hl { background: var(--code-bg); border-radius: 6px; padding: 8px 10px; overflow: auto; }
.hl pre { font-size: 12.5px; line-height: 1.5; white-space: pre; }
.hl .k, .hl .kn, .hl .kd, .hl .kc, .hl .kr, .hl .ow, .hl .kt { color: #a626a4; font-weight: 600; }
.hl .s, .hl .s1, .hl .s2, .hl .sd, .hl .si, .hl .sa { color: #50a14f; }
.hl .mi, .hl .mf, .hl .m { color: #986801; }
.hl .c, .hl .c1, .hl .cm { color: #a0a1a7; font-style: italic; }
.hl .nf, .hl .nb, .hl .fm { color: #4078f2; }
.hl .o { color: #0184bc; }
@media (prefers-color-scheme: dark) {
  .hl .k, .hl .kn, .hl .kd, .hl .kc, .hl .kr, .hl .ow, .hl .kt { color: #c678dd; }
  .hl .s, .hl .s1, .hl .s2, .hl .sd, .hl .si, .hl .sa { color: #98c379; }
  .hl .mi, .hl .mf, .hl .m { color: #d19a66; }
  .hl .c, .hl .c1, .hl .cm { color: #7f848e; }
  .hl .nf, .hl .nb, .hl .fm { color: #61afef; }
  .hl .o { color: #56b6c2; }
}

@media (max-width: 900px) {
  body.problem-page .main { height: auto; overflow: visible; }
  .workspace { flex-direction: column; height: auto; }
  .left { flex-basis: auto !important; }
  .divider { display: none; }
  .side-by-side { grid-template-columns: 1fr; }
  .stats { grid-template-columns: repeat(2, 1fr); }
  body.cheat-open .drawer { width: 90vw; position: fixed; right: 0; z-index: 30; }
}
.answer .hl pre { white-space: pre-wrap; word-break: break-word; }
.group > summary .progress { float: right; font-weight: 400; }