:root {
  --bg: #f5f6f8;
  --surface: #ffffff;
  --surface-2: #f9fafb;
  --ink: #1b2330;
  --ink-2: #3b4655;
  --muted: #667181;
  --line: #e2e6eb;
  --line-2: #d3d9e0;
  --accent: #0f766e;
  --accent-soft: #e6f3f1;
  --accent-ink: #0b5a54;
  --hl: #fff1a8;
  --hl-edge: #e0b400;
  --ok: #1f7a3d;
  --ok-soft: #e7f5ec;
  --bad: #b42331;
  --bad-soft: #fbeaec;
  --shadow: 0 1px 2px rgba(20, 30, 45, .05), 0 4px 16px rgba(20, 30, 45, .04);
  --radius: 12px;
  --c-very_high: #b93815; --c-very_high-bg: #fdece4;
  --c-high: #b42331;      --c-high-bg: #fbeaec;
  --c-rising: #6d3fc0;    --c-rising-bg: #f1ebfc;
  --c-medium: #8a5d00;    --c-medium-bg: #fdf3d8;
  --c-low: #2958a8;       --c-low-bg: #e8effb;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #12161c; --surface: #1a2029; --surface-2: #1f2631; --ink: #e6eaf0; --ink-2: #c7ced8;
    --muted: #97a2b1; --line: #2c3542; --line-2: #394453; --accent: #3fb8a9; --accent-soft: #173532;
    --accent-ink: #7fd8cc; --hl: #4a3f10; --hl-edge: #d9b43a; --ok: #5cc486; --ok-soft: #173424;
    --bad: #f07a85; --bad-soft: #3a1d22; --shadow: none;
    --c-very_high: #ff9a73; --c-very_high-bg: #3b2219; --c-high: #f58a93; --c-high-bg: #3a1d22;
    --c-rising: #b99af0; --c-rising-bg: #2b2140; --c-medium: #e8c060; --c-medium-bg: #36301a;
    --c-low: #8fb3f0; --c-low-bg: #1c2a42;
  }
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0; background: var(--bg); color: var(--ink);
  font-family: "Noto Sans TC", "Microsoft JhengHei", "PingFang TC", system-ui, sans-serif;
  font-size: 16px; line-height: 1.7;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
button, input, select { font: inherit; color: inherit; }
button { cursor: pointer; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

/* ---------- top bar ---------- */
.topbar { position: sticky; top: 0; z-index: 30; background: color-mix(in srgb, var(--surface) 92%, transparent);
  backdrop-filter: blur(10px); border-bottom: 1px solid var(--line); }
.topbar-inner { max-width: 960px; margin: 0 auto; padding: 10px 16px; display: flex; align-items: center; gap: 18px; flex-wrap: wrap; }
.brand { display: flex; align-items: center; gap: 8px; font-weight: 800; color: var(--ink); letter-spacing: .02em; }
.brand:hover { text-decoration: none; }
.brand-mark { width: 26px; height: 26px; border-radius: 7px; display: grid; place-items: center; background: var(--accent); color: #fff; font-size: 14px; }
.nav { display: flex; gap: 4px; }
.nav a { padding: 5px 12px; border-radius: 8px; color: var(--muted); font-weight: 600; }
.nav a:hover { background: var(--surface-2); text-decoration: none; color: var(--ink); }
.nav a.active { background: var(--accent-soft); color: var(--accent-ink); }
.prefs { margin-left: auto; display: flex; align-items: center; gap: 8px; }
.seg { display: inline-flex; border: 1px solid var(--line-2); border-radius: 9px; overflow: hidden; }
.seg button { border: 0; background: transparent; padding: 4px 11px; font-size: 13px; color: var(--muted); }
.seg button + button { border-left: 1px solid var(--line-2); }
.seg button[aria-pressed="true"] { background: var(--accent); color: #fff; }
.toggle { border: 1px solid var(--line-2); background: transparent; border-radius: 9px; padding: 4px 11px; font-size: 13px; color: var(--muted); }
.toggle[aria-pressed="true"] { background: var(--ink-2); border-color: var(--ink-2); color: var(--surface); }

.page { display: block; max-width: 960px; margin: 0 auto; padding: 28px 16px 64px; outline: none; }
.loading, .empty { color: var(--muted); padding: 40px 0; text-align: center; }
.footer { max-width: 960px; margin: 0 auto; padding: 18px 16px 36px; display: flex; gap: 16px; justify-content: space-between; color: var(--muted); font-size: 12px; border-top: 1px solid var(--line); }

/* ---------- headings ---------- */
.crumbs { font-size: 13px; color: var(--muted); display: flex; flex-wrap: wrap; gap: 6px; align-items: center; margin-bottom: 6px; }
.crumbs .sep { opacity: .5; }
h1 { font-size: clamp(26px, 4vw, 34px); line-height: 1.25; margin: 0 0 8px; letter-spacing: .01em; }
.lede { color: var(--ink-2); margin: 0 0 14px; }
.pills { display: flex; flex-wrap: wrap; gap: 8px; }
.pill { font-size: 13px; padding: 3px 10px; border-radius: 999px; background: var(--surface); border: 1px solid var(--line); color: var(--ink-2); }
h2.sec { font-size: 18px; margin: 34px 0 10px; display: flex; align-items: baseline; gap: 10px; }
h2.sec small { font-size: 13px; color: var(--muted); font-weight: 500; }
h2.block { font-size: 16px; margin: 32px 0 10px; color: var(--ink-2); }

/* ---------- toolbar ---------- */
.toolbar { margin: 22px 0 6px; display: grid; gap: 10px; }
.search { position: relative; }
.search input { width: 100%; padding: 10px 14px 10px 38px; border: 1px solid var(--line-2); border-radius: 10px; background: var(--surface); }
.search input:focus { outline: none; border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-soft); }
.search svg { position: absolute; left: 12px; top: 50%; transform: translateY(-50%); color: var(--muted); }
.filter-row { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; }
.chips { display: flex; gap: 6px; flex-wrap: wrap; }
.chip { border: 1px solid var(--line-2); background: var(--surface); border-radius: 999px; padding: 3px 11px; font-size: 13px; color: var(--ink-2); }
.chip .n { color: var(--muted); margin-left: 4px; font-variant-numeric: tabular-nums; }
.chip[aria-pressed="true"] { background: var(--ink-2); border-color: var(--ink-2); color: var(--surface); }
.chip[aria-pressed="true"] .n { color: inherit; opacity: .75; }
.chip:disabled { opacity: .45; cursor: default; }
.sort { margin-left: auto; font-size: 13px; color: var(--muted); display: flex; gap: 6px; align-items: center; }
.sort select { border: 1px solid var(--line-2); border-radius: 8px; background: var(--surface); padding: 3px 8px; }
.count { font-size: 13px; color: var(--muted); }

/* ---------- badge / meta ---------- */
.badge { display: inline-flex; align-items: center; gap: 2px; white-space: nowrap; font-size: 12px; font-weight: 700; padding: 1px 8px; border-radius: 999px; }
.badge.very_high { color: var(--c-very_high); background: var(--c-very_high-bg); }
.badge.high { color: var(--c-high); background: var(--c-high-bg); }
.badge.rising { color: var(--c-rising); background: var(--c-rising-bg); }
.badge.medium { color: var(--c-medium); background: var(--c-medium-bg); }
.badge.low { color: var(--c-low); background: var(--c-low-bg); }
.meta { font-size: 13px; color: var(--muted); font-variant-numeric: tabular-nums; }

/* ---------- knowledge card rows ---------- */
.cards { display: grid; grid-template-columns: minmax(0, 1fr); gap: 8px; }
.kc { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); box-shadow: var(--shadow); }
.kc-head { display: flex; gap: 12px; align-items: center; width: 100%; padding: 12px 16px; border: 0; background: transparent; text-align: left; color: inherit; border-radius: var(--radius); }
a.kc-head:hover { text-decoration: none; }
.kc-head:hover .kc-title { color: var(--accent-ink); }
.kc-main { flex: 1; min-width: 0; }
.kc-title { font-size: 16px; font-weight: 700; margin: 0 0 3px; line-height: 1.45; }
.kc-sub { display: flex; flex-wrap: wrap; gap: 4px 10px; align-items: center; }
.kc-chev { flex: none; width: 28px; height: 28px; display: grid; place-items: center; border-radius: 50%; color: var(--muted); transition: transform .15s; }
.kc.open .kc-chev { transform: rotate(180deg); }
.kc-body { display: none; padding: 0 16px 16px; }
.kc.open .kc-body { display: block; }
.kc.open { border-color: var(--line-2); }
.body-actions { display: flex; gap: 8px; flex-wrap: wrap; margin-top: 14px; }

.btn { display: inline-flex; align-items: center; gap: 6px; border: 1px solid var(--line-2); background: var(--surface); color: var(--ink-2); border-radius: 9px; padding: 5px 12px; font-size: 14px; font-weight: 600; }
.btn:hover { border-color: var(--accent); color: var(--accent-ink); text-decoration: none; }
.btn.primary { background: var(--accent); border-color: var(--accent); color: #fff; }
.btn.primary:hover { color: #fff; filter: brightness(1.07); }
.btn.small { font-size: 13px; padding: 3px 10px; }
.btn[aria-pressed="true"] { background: var(--hl); border-color: var(--hl-edge); color: var(--ink); }

/* ---------- card content ---------- */
.card-content { background: var(--surface-2); border: 1px solid var(--line); border-radius: 10px; padding: 14px 16px; font-size: 15.5px; line-height: 1.8; overflow-x: auto; }
.card-page .card-content { background: var(--surface); font-size: 16px; padding: 18px 20px; }
.card-content > div:first-child { font-weight: 700; }
.card-content .indent { margin-left: 1.6em; }
.card-content table { border-collapse: collapse; width: 100%; font-size: 14px; margin: 6px 0; }
.card-content td, .card-content th { border: 1px solid var(--line-2); padding: 3px 7px; vertical-align: top; }
.card-content img { max-width: 100%; height: auto; border-radius: 6px; }
.card-content .extra { margin-top: 12px; padding-top: 10px; border-top: 1px dashed var(--line-2); color: var(--ink-2); font-size: 14px; }
.cz { color: var(--accent-ink); font-weight: 600; border-bottom: 1.5px solid color-mix(in srgb, var(--accent) 45%, transparent); }
.cloze-hidden .cz:not(.shown) { color: transparent; background: var(--accent-soft); border-bottom-color: var(--accent); cursor: pointer; border-radius: 3px; user-select: none; }
.cloze-hidden .cz:not(.shown) img { visibility: hidden; }
.ln { transition: background .2s; border-radius: 3px; }
.ln.hl { background: var(--hl); box-shadow: -4px 0 0 var(--hl-edge); padding: 1px 2px; }
.hl-banner { display: flex; gap: 10px; align-items: center; flex-wrap: wrap; font-size: 13px; background: var(--hl); color: var(--ink); border-left: 4px solid var(--hl-edge); padding: 6px 12px; border-radius: 8px; margin: 12px 0 10px; }
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) .hl-banner { color: var(--ink); } }
.hl-banner button { margin-left: auto; border: 0; background: transparent; color: inherit; text-decoration: underline; font-size: 13px; }

/* ---------- card page ---------- */
.card-page .head-badges { display: flex; flex-wrap: wrap; align-items: center; gap: 8px 12px; margin: 4px 0 12px; }
.strip { display: grid; grid-template-columns: repeat(var(--n, 10), minmax(0, 1fr)); gap: 4px; margin: 6px 0 4px; max-width: 560px; }
.strip .s { text-align: center; font-size: 10.5px; color: var(--muted); font-variant-numeric: tabular-nums; }
.strip .s i { display: block; height: 10px; border-radius: 3px; background: var(--line); margin-bottom: 3px; }
.strip .s.hit i { background: var(--accent); }
.strip .s.recent i { outline: 1.5px solid var(--line-2); outline-offset: 1px; }
.strip-note { font-size: 12px; color: var(--muted); }
.pager { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; margin-top: 36px; }
.pager a { display: block; padding: 10px 14px; border: 1px solid var(--line); border-radius: 10px; background: var(--surface); color: var(--ink); min-width: 0; }
.pager a:hover { border-color: var(--accent); text-decoration: none; }
.pager small { display: block; color: var(--muted); font-size: 12px; }
.pager span { display: block; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; font-weight: 600; }
.pager .next { text-align: right; grid-column: 2; }

.qlabel { font-weight: 700; font-size: 14px; white-space: nowrap; font-variant-numeric: tabular-nums; }
.qstem { flex: 1 1 260px; min-width: 0; color: var(--ink-2); font-size: 14px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.mark.ok { color: var(--ok); background: var(--ok-soft); }
.mark.bad { color: var(--bad); background: var(--bad-soft); }

/* ---------- question block ---------- */
.qblock { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 18px 20px; box-shadow: var(--shadow); }
.q-stem { font-size: 16.5px; margin: 0 0 12px; }
.q-images { display: flex; flex-wrap: wrap; gap: 10px; margin: 0 0 12px; }
.q-images img { max-width: min(100%, 420px); height: auto; border: 1px solid var(--line); border-radius: 8px; background: #fff; }
.opts { display: grid; gap: 7px; }
.opt { display: flex; gap: 10px; align-items: flex-start; width: 100%; text-align: left; padding: 9px 12px; border: 1px solid var(--line-2); border-radius: 10px; background: var(--surface); color: var(--ink); line-height: 1.6; }
.opt:hover:not(:disabled) { border-color: var(--accent); }
.opt:disabled { cursor: default; }
.opt .k { flex: none; width: 24px; height: 24px; border-radius: 50%; display: grid; place-items: center; font-size: 13px; font-weight: 700; background: var(--surface-2); border: 1px solid var(--line-2); }
.opt.correct { border-color: var(--ok); background: var(--ok-soft); }
.opt.correct .k { background: var(--ok); color: #fff; border-color: var(--ok); }
.opt.wrong { border-color: var(--bad); background: var(--bad-soft); }
.opt.wrong .k { background: var(--bad); color: #fff; border-color: var(--bad); }
.q-actions { display: flex; gap: 8px; flex-wrap: wrap; margin-top: 12px; align-items: center; }
.verdict { font-weight: 700; }
.verdict.ok { color: var(--ok); } .verdict.bad { color: var(--bad); }
.reveal { margin-top: 16px; padding-top: 14px; border-top: 1px solid var(--line); }
.answer-line { font-weight: 700; margin-bottom: 6px; }
.explanation { color: var(--ink-2); font-size: 15px; }
.explanation-title { font-size: 13px; font-weight: 700; color: var(--muted); margin: 10px 0 2px; letter-spacing: .05em; }
.related { margin-top: 18px; }
.related h3, .reveal h3 { font-size: 14px; color: var(--muted); margin: 0 0 8px; letter-spacing: .03em; }
.rc { border: 1px solid var(--line); border-radius: 10px; background: var(--surface); margin-bottom: 6px; }
.rc-head { display: flex; gap: 10px; align-items: center; padding: 8px 12px; flex-wrap: wrap; }
.rc-body { padding: 0 12px 12px; }

/* ---------- question list ---------- */
.qnav { display: flex; justify-content: space-between; gap: 10px; margin: 18px 0 0; flex-wrap: wrap; }

/* ---------- QA ---------- */
.qa table { border-collapse: collapse; width: 100%; font-size: 13px; background: var(--surface); }
.qa td, .qa th { border: 1px solid var(--line); padding: 5px 8px; text-align: left; vertical-align: top; }
.qa th { background: var(--surface-2); font-weight: 600; }
.qa .num { text-align: right; font-variant-numeric: tabular-nums; }
.qa .scroll { overflow-x: auto; }
.qa h2 { font-size: 16px; margin: 28px 0 8px; }

@media (max-width: 640px) {
  .topbar-inner { gap: 10px; }
  .prefs { margin-left: 0; width: 100%; }
  .page { padding-top: 20px; }
  .card-page .card-content { padding: 14px; }
  .qblock { padding: 14px; }
  .sort { margin-left: 0; }
  .pager { grid-template-columns: 1fr; }
  .pager .next { grid-column: 1; }
}
.group-ctx { background: var(--surface-2); border: 1px dashed var(--line-2); border-radius: 10px; padding: 8px 12px; margin-bottom: 12px; color: var(--ink-2); font-size: 15px; }
.group-ctx .explanation-title { margin-top: 0; }

/* ---------- question blocks (shown directly under cards and in the question list) ---------- */
.qlist { display: grid; grid-template-columns: minmax(0, 1fr); gap: 12px; }
.q-head { display: flex; gap: 8px; align-items: center; margin-bottom: 8px; }
.qlabel { font-weight: 700; font-size: 14px; color: var(--accent-ink); font-variant-numeric: tabular-nums; }
.mark { font-size: 12px; font-weight: 700; padding: 0 6px; border-radius: 6px; }
.qblock.active { border-color: var(--hl-edge); box-shadow: -3px 0 0 var(--hl-edge); }
.kc-body .qblock, .card-page .qblock { box-shadow: none; }
.kc-body .qblock { background: var(--surface-2); padding: 14px 16px; }
.rc-head { display: flex; gap: 8px; align-items: center; padding: 6px 8px 6px 4px; }
.rc-toggle { flex: 1; min-width: 0; display: flex; gap: 10px; align-items: center; border: 0; background: transparent; padding: 4px 8px; text-align: left; color: var(--ink); border-radius: 8px; }
.rc-toggle:hover .rc-title { color: var(--accent-ink); }
.rc-title { flex: 1; min-width: 0; font-weight: 700; font-size: 15px; }
.rc-toggle .kc-chev { transform: rotate(0deg); }
.rc.open .rc-toggle .kc-chev { transform: rotate(180deg); }
.rc-links { display: grid; gap: 8px; justify-items: start; }
.rc-links .btn { white-space: normal; text-align: left; }

/* ---------- jump to a card and back to the question ---------- */
.qblock { scroll-margin-top: 76px; }
.qblock.flash { animation: flash 1.6s ease-out; }
@keyframes flash { 0%, 30% { box-shadow: 0 0 0 3px var(--accent); } 100% { box-shadow: 0 0 0 0 transparent; } }
.back-btn { margin-bottom: 14px; }
.float-back { position: fixed; right: 16px; bottom: 16px; z-index: 40; border: 0; border-radius: 999px; padding: 10px 16px;
  background: var(--accent); color: #fff; font-weight: 700; font-size: 14px; box-shadow: 0 6px 20px rgba(0, 0, 0, .18); max-width: calc(100vw - 32px); }
.float-back:hover { filter: brightness(1.08); }
.rc-head .btn.small { flex: none; }

/* ---------- collapsible questions in the question list ---------- */
.sec-row { display: flex; align-items: baseline; justify-content: space-between; gap: 12px; margin: 34px 0 10px; scroll-margin-top: 76px; }
.sec-row h2.sec { margin: 0; }
.qitem { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); box-shadow: var(--shadow); scroll-margin-top: 76px; }
.qitem.open { border-color: var(--line-2); }
.qitem:has(.qblock.active) { border-color: var(--hl-edge); box-shadow: -3px 0 0 var(--hl-edge); }
.qitem-head { display: flex; gap: 10px; align-items: center; width: 100%; padding: 12px 16px; border: 0; background: transparent; text-align: left; color: inherit; border-radius: var(--radius); }
.qitem-head .qlabel { flex: none; }
.qitem-head .mark { flex: none; }
.qitem-head .qstem { flex: 1; min-width: 0; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; color: var(--ink-2); font-size: 15px; }
.qitem-head:hover .qstem { color: var(--ink); }
.qitem-head .kc-chev { flex: none; }
.qitem.open .qitem-head .kc-chev { transform: rotate(180deg); }
.qitem .qblock { border: 0; box-shadow: none; background: transparent; padding: 0 16px 16px; }
.qitem .qblock.active { box-shadow: none; }
.qitem.flash { animation: flash 1.6s ease-out; }