/* TOEIC Part 5 & 6 Grammar — exam practice for adult learners.

   A teacher drives this in a one-to-one or small-group session, usually on one
   laptop turned sideways or a shared screen. Design notes:

   - English leads and is the only thing on screen by default. Traditional
     Chinese sits behind a small 中 chip, so the learner tries the English
     first and the safety net is one tap away. Headings, instructions, table
     headers and the contents list stay bilingual — those are scaffolding, not
     comprehension practice.
   - Questions look like the test. Four options lettered A to D, one blank per
     sentence, and in Part 6 the questions sit under the passage exactly as
     they do on the paper.
   - A wrong option dims and stays put; only the right one fills the blank, and
     filling it opens the explanation. There is no score and no streak — the
     count under a set is how many blanks are filled, nothing more.
   - Light theme only. It is read side by side in a lit room, and the source
     handouts are the reference.
   - Text sizes are set for adults reading at arm's length on a shared screen,
     a size up from a personal document. */

:root {
  --paper: #f7f6f2;
  --card: #ffffff;
  --ink: #1c2430;
  --ink-soft: #566171;
  --ink-faint: #8b95a3;

  --navy: #1d3f6e;
  --navy-soft: #eaf0f8;
  --navy-line: #c2d3e7;

  --gold: #a1741a;
  --gold-soft: #fbf1da;
  --gold-line: #f2c14e;

  --good: #2c7a58;
  --good-soft: #e4f2ea;
  --good-line: #a8d6be;

  --bad: #a6402f;
  --bad-soft: #fbeae6;

  --line: #e3e0d8;
  --rule: #cdc8bc;

  --font-en: "Iowan Old Style", "Palatino Linotype", Palatino, Charter, Georgia, "Times New Roman", serif;
  --font-zh: "PingFang TC", "Heiti TC", "Noto Sans TC", "Microsoft JhengHei", "Hiragino Sans CNS", sans-serif;
  --font-ui: -apple-system, BlinkMacSystemFont, "Segoe UI", system-ui, sans-serif;
  --font-mono: ui-monospace, "SF Mono", Menlo, Consolas, monospace;

  --bar-h: 54px;
  --measure: 46rem;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; scroll-padding-top: calc(var(--bar-h) + 16px); }

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--font-en);
  font-size: 18px;
  line-height: 1.6;
  -webkit-text-size-adjust: 100%;
}

/* ---------------- the Chinese layer ----------------

   Hidden everywhere by default. A line opens on its own when tapped; the 中文
   switch in the bar opens all of them at once, at which point the individual
   chips are just clutter and go away. */

.zh {
  display: none;
  font-family: var(--font-zh);
  font-size: 0.82em;
  line-height: 1.7;
  color: var(--ink-soft);
  letter-spacing: .01em;
}

.open .zh,
body.zh-all .zh { display: block; }

.zh-chip {
  font-family: var(--font-zh);
  font-size: 11px;
  line-height: 1;
  vertical-align: 2px;
  margin-left: 6px;
  padding: 3px 5px;
  color: var(--ink-faint);
  background: transparent;
  border: 1px solid var(--line);
  border-radius: 5px;
  cursor: pointer;
  transition: color .12s, border-color .12s, background .12s;
}
.zh-chip:hover { color: var(--navy); border-color: var(--navy-line); background: var(--navy-soft); }
.open > .zh-chip,
.open .en > .zh-chip { opacity: .35; }
body.zh-all .zh-chip { display: none; }

/* Scaffolding stays bilingual at all times: it tells you what to do rather
   than asking you to understand it. */
.hint-zh,
.source .zh,
.toc .t .zh,
.label .zh,
.step-head .zh,
.why .zh,
.steps .zh,
.tier-head .zh,
.tiers li .zh,
.kind .zh,
.table-wrap th .zh { display: block; }

[data-zh] { cursor: pointer; }
.pair p { margin: 0; }
.pair .zh { margin-top: 4px; }

.skip { position: absolute; left: -9999px; }
.skip:focus {
  left: 12px; top: 12px; z-index: 40;
  background: var(--card); padding: 10px 16px; border-radius: 8px;
}

:focus-visible { outline: 2px solid var(--navy); outline-offset: 2px; }

/* ---------------- top bar ---------------- */

.bar {
  position: sticky;
  top: 0;
  z-index: 30;
  height: var(--bar-h);
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 0 16px;
  background: rgba(247, 246, 242, .93);
  backdrop-filter: saturate(1.6) blur(10px);
  border-bottom: 1px solid var(--line);
}

.bar-title {
  flex: 1;
  margin: 0;
  min-width: 0;
  font-size: 15px;
  font-weight: 600;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.bar-title span {
  font-family: var(--font-zh);
  font-size: 13px;
  font-weight: 400;
  color: var(--ink-faint);
  margin-left: 8px;
}

.bar-btn {
  flex: none;
  font-family: var(--font-ui);
  font-size: 13px;
  color: var(--navy);
  background: transparent;
  border: 1px solid var(--navy-line);
  border-radius: 7px;
  padding: 6px 11px;
  cursor: pointer;
}
.bar-btn:hover { background: var(--navy-soft); }
.bar-btn-quiet { color: var(--ink-soft); border-color: var(--line); font-size: 15px; padding: 4px 9px; }
.bar-btn-zh { font-family: var(--font-zh); }
.bar-btn-zh[aria-pressed="true"] { background: var(--navy); border-color: var(--navy); color: #fff; }

#clock {
  font-family: var(--font-ui);
  font-variant-numeric: tabular-nums;
  min-width: 42px;
  text-align: center;
}
#clock.running { color: var(--navy); border-color: var(--navy-line); background: var(--navy-soft); }

@media (min-width: 900px) { #navToggle { display: none; } }

/* ---------------- shell + contents ---------------- */

.shell {
  display: grid;
  grid-template-columns: 1fr;
  max-width: 76rem;
  margin: 0 auto;
  padding: 0 20px;
}

@media (min-width: 900px) {
  .shell { grid-template-columns: 15rem minmax(0, 1fr); gap: 44px; padding: 0 28px; }
}

.toc { font-family: var(--font-ui); }

@media (min-width: 900px) {
  .toc {
    position: sticky;
    top: var(--bar-h);
    max-height: calc(100vh - var(--bar-h));
    overflow-y: auto;
    padding: 30px 0 40px;
    scrollbar-width: thin;
  }
}

.toc-head {
  margin: 0 0 10px;
  font-size: 11px;
  font-weight: 600;
  letter-spacing: .1em;
  text-transform: uppercase;
  color: var(--ink-faint);
}

.toc ul { list-style: none; margin: 0; padding: 0; }

.toc a {
  display: grid;
  grid-template-columns: 1.4rem 1fr;
  gap: 8px;
  padding: 8px 10px 8px 6px;
  border-radius: 7px;
  text-decoration: none;
  color: var(--ink-soft);
  border-left: 2px solid transparent;
}
.toc a:hover { background: var(--navy-soft); color: var(--ink); }
.toc a .n {
  font-size: 12px;
  font-variant-numeric: tabular-nums;
  color: var(--ink-faint);
  text-align: right;
  padding-top: 3px;
}
.toc a .t .en { display: block; font-size: 13.5px; line-height: 1.35; }
.toc a .t .zh { font-size: 11.5px; color: var(--ink-faint); }
.toc a.here {
  background: var(--navy-soft);
  border-left-color: var(--navy);
  color: var(--navy);
}
.toc a.here .n, .toc a.here .t .zh { color: var(--navy); }
.toc a.here .t .en { font-weight: 600; }

@media (max-width: 899px) {
  #nav {
    position: fixed;
    top: var(--bar-h);
    left: 0; right: 0;
    z-index: 25;
    max-height: min(70vh, 30rem);
    overflow-y: auto;
    background: var(--card);
    border-bottom: 1px solid var(--line);
    box-shadow: 0 12px 24px rgba(28, 36, 48, .12);
    padding: 14px 18px 18px;
    display: none;
  }
  body.nav-open #nav { display: block; }
  body.nav-open .nav-scrim {
    display: block;
    position: fixed;
    inset: var(--bar-h) 0 0;
    z-index: 24;
    background: rgba(28, 36, 48, .25);
  }
}

main { max-width: var(--measure); padding-bottom: 6rem; }

/* ---------------- cover ---------------- */

.cover { padding: 40px 0 26px; }

.kicker {
  margin: 0 0 10px;
  font-family: var(--font-zh);
  font-size: 13px;
  letter-spacing: .16em;
  color: var(--gold);
}

.cover h1 {
  margin: 0 0 18px;
  font-size: clamp(28px, 5vw, 40px);
  line-height: 1.18;
  letter-spacing: -.01em;
}
.cover h1 .zh { font-size: 19px; font-weight: 400; margin-top: 6px; }

.cover-intro .en { font-size: 21px; line-height: 1.55; }

.goals {
  margin: 22px 0;
  padding: 18px 22px;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 12px;
}
.goals-intro .en { font-size: 15px; font-weight: 600; }
.goals-intro { margin-bottom: 8px; }
.goals ol { margin: 0; padding-left: 1.3rem; }
.goals li { margin: 7px 0; font-size: 16.5px; }
.goals li::marker { color: var(--ink-faint); font-size: 14px; }

.format .en { font-size: 15.5px; color: var(--ink-soft); }
.format {
  padding: 14px 18px;
  border-left: 3px solid var(--gold-line);
  background: var(--gold-soft);
  border-radius: 0 8px 8px 0;
}

.source {
  margin: 26px 0 0;
  font-size: 12.5px;
  color: var(--ink-faint);
  line-height: 1.5;
}
.source .zh { font-size: 12px; }

/* ---------------- section ---------------- */

.step {
  padding-top: 34px;
  margin-top: 34px;
  border-top: 1px solid var(--rule);
}

.step-head {
  display: grid;
  grid-template-columns: 2.1rem 1fr auto;
  align-items: baseline;
  gap: 10px;
  margin: 0 0 20px;
  font-size: 26px;
  line-height: 1.25;
}
.step-head .n {
  font-family: var(--font-ui);
  font-size: 13px;
  font-weight: 600;
  color: var(--gold);
  border: 1px solid var(--gold-line);
  border-radius: 6px;
  text-align: center;
  padding: 2px 0;
}
.step-head .zh { font-size: 16px; font-weight: 400; margin-top: 2px; }
.step-head .p6 {
  font-family: var(--font-ui);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: .06em;
  color: var(--navy);
  background: var(--navy-soft);
  border: 1px solid var(--navy-line);
  border-radius: 20px;
  padding: 3px 10px;
}

.lead { margin: 0 0 20px; }
.lead .en { font-size: 18.5px; font-style: italic; color: var(--ink-soft); }

.rule { margin: 18px 0; }
.rule .en { font-size: 17.5px; }

.label {
  margin: 0 0 10px;
  font-family: var(--font-ui);
  font-size: 13px;
  font-weight: 600;
  letter-spacing: .04em;
  text-transform: uppercase;
  color: var(--ink-faint);
}
.label .zh {
  font-size: 12px;
  text-transform: none;
  letter-spacing: 0;
  margin-top: 1px;
}

.hint {
  margin: 0 0 12px;
  font-family: var(--font-ui);
  font-size: 13.5px;
  color: var(--ink-soft);
}
.hint-zh { font-family: var(--font-zh); font-size: 12.5px; color: var(--ink-faint); }

/* ---------------- speak buttons ---------------- */

.say {
  border: none;
  background: transparent;
  cursor: pointer;
  font-size: 15px;
  line-height: 1;
  padding: 2px 4px;
  margin-left: 4px;
  opacity: .5;
  transition: opacity .12s;
}
.say:hover { opacity: 1; }
.say-quiet { font-size: 13px; opacity: .3; }
.say-quiet:hover { opacity: .9; }

/* ---------------- formula ---------------- */

.formula {
  margin: 16px 0;
  padding: 16px 20px;
  background: var(--card);
  border: 1px solid var(--line);
  border-left: 3px solid var(--gold-line);
  border-radius: 0 12px 12px 0;
}

.f-head { margin: 0 0 8px; display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.f-n {
  font-family: var(--font-ui);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: .06em;
  color: var(--gold);
  background: var(--gold-soft);
  border-radius: 20px;
  padding: 3px 10px;
  white-space: nowrap;
}
.f-pattern {
  font-family: var(--font-mono);
  font-size: 16px;
  font-weight: 600;
  color: var(--navy);
  letter-spacing: -.01em;
}

.f-rule .en { font-size: 15.5px; color: var(--ink-soft); }

.reveal {
  margin-top: 10px;
  font-family: var(--font-ui);
  font-size: 12.5px;
  color: var(--navy);
  background: transparent;
  border: 1px solid var(--navy-line);
  border-radius: 20px;
  padding: 4px 12px;
  cursor: pointer;
}
.reveal:hover { background: var(--navy-soft); }

.f-egs { list-style: none; margin: 12px 0 0; padding: 0; }
.f-egs li {
  padding: 8px 0;
  border-top: 1px dotted var(--line);
  font-size: 16px;
}

/* ---------------- tables ---------------- */

.table-wrap { margin: 20px 0; overflow-x: auto; }

.table-wrap table {
  width: 100%;
  border-collapse: collapse;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 10px;
  overflow: hidden;
  font-size: 15.5px;
}

.table-wrap th {
  text-align: left;
  padding: 9px 14px;
  background: var(--navy-soft);
  border-bottom: 1px solid var(--navy-line);
  font-family: var(--font-ui);
  font-size: 12px;
  font-weight: 600;
  letter-spacing: .04em;
  text-transform: uppercase;
  color: var(--navy);
}
.table-wrap th .zh {
  font-size: 11.5px;
  text-transform: none;
  letter-spacing: 0;
  color: var(--navy);
  opacity: .75;
}

.table-wrap td {
  padding: 9px 14px;
  border-top: 1px solid var(--line);
  vertical-align: top;
}
.table-wrap tbody tr:first-child td { border-top: none; }
.table-wrap tbody tr[data-zh]:hover { background: var(--navy-soft); }
.table-wrap td .en { display: block; }

/* A phrase table is a self-test: the meaning column stays covered until the
   row is tapped, and shows as a rule until then. */
.td-zh { min-width: 7rem; }
.td-zh::after {
  content: "";
  display: block;
  width: 4.5rem;
  border-bottom: 1px solid var(--rule);
  margin-top: .7em;
}
tr.open .td-zh::after,
body.zh-all .td-zh::after { display: none; }

.t-family table { font-family: var(--font-ui); font-size: 14.5px; }
.t-family td { white-space: nowrap; }

/* ---------------- example sentences ---------------- */

.egs { margin: 20px 0; }
.egs ol { margin: 0; padding-left: 1.6rem; }
.egs li { margin: 10px 0; font-size: 17px; }
.egs li::marker { font-family: var(--font-ui); font-size: 13px; color: var(--ink-faint); }

/* ---------------- collocation chips ---------------- */

.phrases { margin: 22px 0; }

.chip-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 8px;
  align-items: start;
  grid-template-columns: repeat(auto-fill, minmax(15rem, 1fr));
}

.pchip {
  padding: 9px 13px;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 9px;
}
.pchip:hover { border-color: var(--navy-line); }
.pchip .en { font-size: 16px; }
.pchip .zh { font-size: 13px; }

/* ---------------- contrast ---------------- */

.contrast ul { list-style: none; margin: 0; padding: 0; }
.contrast li {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: 12px;
  padding: 10px 0;
  border-top: 1px dotted var(--line);
}
.contrast li:first-child { border-top: none; }
.contrast .side { padding: 8px 12px; background: var(--card); border: 1px solid var(--line); border-radius: 9px; }
.contrast .side .en { font-size: 16px; }
.contrast .vs { color: var(--ink-faint); font-size: 15px; }

@media (max-width: 560px) {
  .contrast li { grid-template-columns: 1fr; }
  .contrast .vs { display: none; }
}

/* ---------------- note ---------------- */

.note {
  margin: 20px 0;
  padding: 16px 20px;
  background: var(--gold-soft);
  border: 1px solid var(--gold-line);
  border-radius: 12px;
}
.note h4 {
  margin: 0 0 8px;
  font-family: var(--font-ui);
  font-size: 14px;
  font-weight: 600;
  color: var(--gold);
}
.note h4 .zh { font-size: 12.5px; font-weight: 400; margin-top: 1px; }
.note .en { font-size: 16px; }

.ex {
  margin: 10px 0 0;
  padding: 7px 12px 7px 30px;
  background: rgba(255, 255, 255, .7);
  border-radius: 8px;
  font-size: 15.5px;
  position: relative;
}
.ex::before {
  position: absolute;
  left: 11px;
  font-family: var(--font-ui);
  font-weight: 700;
}
.ex-good { color: var(--good); }
.ex-good::before { content: "✓"; }
.ex-bad { color: var(--bad); text-decoration: line-through; text-decoration-color: rgba(166, 64, 47, .35); }
.ex-bad::before { content: "✕"; text-decoration: none; }

/* ---------------- steps ---------------- */

.steps { margin: 20px 0; }
.steps ol {
  margin: 0;
  padding: 0;
  list-style: none;
  counter-reset: s;
}
.steps li {
  counter-increment: s;
  position: relative;
  padding: 9px 0 9px 2.4rem;
  border-top: 1px dotted var(--line);
  font-size: 16.5px;
}
.steps li:first-child { border-top: none; }
.steps li::before {
  content: counter(s);
  position: absolute;
  left: 0;
  top: 10px;
  width: 1.6rem;
  height: 1.6rem;
  line-height: 1.55rem;
  text-align: center;
  font-family: var(--font-ui);
  font-size: 12px;
  font-weight: 600;
  color: var(--navy);
  background: var(--navy-soft);
  border-radius: 50%;
}
.steps .zh { font-size: 13.5px; }

/* ---------------- questions ---------------- */

.activity { margin: 26px 0; }

.q {
  padding: 14px 0;
  border-top: 1px dotted var(--line);
}
.q:first-of-type { border-top: none; }

.q-line {
  display: flex;
  align-items: baseline;
  gap: 9px;
  margin: 0 0 10px;
  font-size: 17px;
  line-height: 1.6;
}
.q-n {
  flex: none;
  font-family: var(--font-ui);
  font-size: 12px;
  font-weight: 600;
  color: var(--ink-faint);
  font-variant-numeric: tabular-nums;
  min-width: 1.1rem;
}
.q-text { flex: 1; }

/* The blank. It is drawn rather than typed into, and the answer lands in it. */
.slot {
  display: inline-block;
  min-width: 6.5rem;
  padding: 0 .35em;
  border-bottom: 1.5px solid var(--rule);
  text-align: center;
  font-weight: 600;
  color: var(--navy);
  vertical-align: baseline;
}
.q.solved .slot { border-bottom-color: var(--good-line); color: var(--good); }

/* Four options in a 2 × 2 block. An even grid reads faster than a ragged one,
   and the four never end up as three and a stray. */
.opts {
  list-style: none;
  margin: 0;
  padding: 0 0 0 1.9rem;
  display: grid;
  gap: 7px;
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

@media (max-width: 520px) {
  .opts { grid-template-columns: 1fr; }
}

.opt {
  display: flex;
  align-items: baseline;
  gap: 8px;
  width: 100%;
  text-align: left;
  font-family: var(--font-en);
  font-size: 16px;
  color: var(--ink);
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 9px;
  padding: 8px 12px;
  cursor: pointer;
  transition: border-color .12s, background .12s, opacity .12s;
}
.opt:hover { border-color: var(--navy-line); background: var(--navy-soft); }

.lab {
  flex: none;
  font-family: var(--font-ui);
  font-size: 11px;
  font-weight: 700;
  color: var(--ink-faint);
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: 1px 5px;
}

.opt.out {
  opacity: .4;
  background: var(--paper);
  cursor: default;
}
.opt.out:hover { border-color: var(--line); background: var(--paper); }

.opt.right {
  background: var(--good-soft);
  border-color: var(--good-line);
  color: var(--good);
  font-weight: 600;
}
.opt.right .lab { color: var(--good); border-color: var(--good-line); }
.q.solved .opt { cursor: default; }
.q.solved .opt:not(.right):not(.out) { opacity: .55; }

/* The explanation is written for after the answer, so it waits. */
.why {
  display: none;
  margin: 10px 0 0 1.9rem;
  padding: 9px 14px;
  background: var(--good-soft);
  border-left: 3px solid var(--good-line);
  border-radius: 0 8px 8px 0;
  font-size: 15px;
  color: var(--ink-soft);
}
.q.solved .why { display: block; }
.why .zh { font-size: 13.5px; margin-top: 3px; }

.tally {
  margin: 14px 0 0;
  font-family: var(--font-ui);
  font-size: 12.5px;
  color: var(--ink-faint);
  font-variant-numeric: tabular-nums;
}
.tally .done { font-weight: 700; color: var(--ink-soft); }
.all-done .tally .done { color: var(--good); }
.pace {
  font-family: var(--font-zh);
  margin-left: 10px;
  padding-left: 10px;
  border-left: 1px solid var(--line);
}

@keyframes nope {
  0%, 100% { transform: translateX(0); }
  20% { transform: translateX(-5px); }
  40% { transform: translateX(5px); }
  60% { transform: translateX(-3px); }
  80% { transform: translateX(3px); }
}
.no { animation: nope .38s ease; }

/* ---------------- Part 6 ---------------- */

.letter {
  margin: 0 0 18px;
  padding: 18px 22px;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 12px;
}

.kind {
  margin: 0 0 12px;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--line);
  font-family: var(--font-ui);
  font-size: 12.5px;
  font-weight: 600;
  color: var(--ink-faint);
}
.kind .zh { font-size: 11.5px; font-weight: 400; }

.passage p { margin: 0 0 .9em; font-size: 17px; line-height: 1.75; }
.passage p:last-child { margin-bottom: 0; }

.b6 { white-space: nowrap; }
.b6-long { white-space: normal; }
.b6-n {
  font-family: var(--font-ui);
  font-size: 10.5px;
  font-weight: 700;
  color: var(--navy);
  background: var(--navy-soft);
  border-radius: 4px;
  padding: 1px 4px;
  vertical-align: 2px;
  margin-right: 3px;
}
.b6 .slot { min-width: 5.5rem; }
.b6-long .slot { min-width: 12rem; white-space: normal; }
.b6.filled .slot { border-bottom-color: transparent; }
.b6.filled .b6-n { opacity: .45; }

.q6-qs { list-style: none; margin: 0; padding: 0; counter-reset: b; }
.q6-qs .q { counter-increment: b; }
.q6-qs .opts { padding-left: 1.9rem; }
.q6-qs .q::before {
  content: counter(b);
  float: left;
  width: 1.1rem;
  font-family: var(--font-ui);
  font-size: 12px;
  font-weight: 600;
  color: var(--ink-faint);
  padding-top: 10px;
}

.q-kind {
  margin: 0 0 8px 1.9rem;
  font-family: var(--font-ui);
  font-size: 13px;
  color: var(--ink-soft);
}

/* A whole-sentence option needs a row of its own to stay readable. */
.q-long .opts { grid-template-columns: 1fr; }
.q-long .opt { font-size: 15.5px; }

/* ---------------- formula cards ---------------- */

/* align-items: start, so opening one card does not inflate the closed one
   sitting beside it into a large empty box. */
.fcards {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 10px;
  align-items: start;
  grid-template-columns: repeat(auto-fill, minmax(17rem, 1fr));
}

.fcard {
  padding: 12px 15px;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 11px;
  cursor: pointer;
  transition: border-color .12s, box-shadow .12s;
}
.fcard:hover { border-color: var(--gold-line); box-shadow: 0 2px 10px rgba(28, 36, 48, .06); }

.fcard-head { display: flex; align-items: baseline; gap: 9px; margin: 0; }
.fcard-n {
  flex: none;
  font-family: var(--font-ui);
  font-size: 11px;
  font-weight: 700;
  color: var(--gold);
  background: var(--gold-soft);
  border-radius: 5px;
  padding: 2px 6px;
  font-variant-numeric: tabular-nums;
}
.fcard-head code {
  font-family: var(--font-mono);
  font-size: 14.5px;
  font-weight: 600;
  color: var(--navy);
  line-height: 1.4;
}

.fcard-back { display: none; margin-top: 10px; padding-top: 10px; border-top: 1px dotted var(--line); }
.fcard.open .fcard-back { display: block; }
.fcard-eg { margin: 0; font-size: 15.5px; color: var(--ink); }
.fcard-zh { margin: 3px 0 0; font-family: var(--font-zh); font-size: 13px; color: var(--ink-soft); }
.fcard-to {
  display: inline-block;
  margin-top: 8px;
  font-family: var(--font-ui);
  font-size: 12px;
  color: var(--navy);
  text-decoration: none;
}
.fcard-to:hover { text-decoration: underline; }

/* ---------------- tiers ---------------- */

.tiers { margin: 22px 0; }
.tiers-lead { margin-bottom: 14px; }
.tiers-lead .en { font-size: 16.5px; color: var(--ink-soft); }

.tier {
  margin: 12px 0;
  padding: 14px 18px;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 11px;
}
.tier-head {
  margin: 0 0 8px;
  font-family: var(--font-ui);
  font-size: 13px;
  font-weight: 600;
  color: var(--navy);
}
.tier-head .zh { font-size: 12px; font-weight: 400; color: var(--ink-faint); }

.tier ol { margin: 0; padding-left: 1.4rem; }
.tier li { margin: 5px 0; font-size: 16px; }
.tier li::marker { font-family: var(--font-ui); font-size: 12.5px; color: var(--ink-faint); }
.tier li a { color: inherit; text-decoration: none; border-bottom: 1px solid var(--navy-line); }
.tier li a:hover { color: var(--navy); background: var(--navy-soft); }
.tier li .zh { font-size: 13px; }

/* ---------------- teacher panel ---------------- */

.panel {
  position: fixed;
  top: calc(var(--bar-h) + 8px);
  right: 12px;
  z-index: 35;
  width: min(22rem, calc(100vw - 24px));
  max-height: calc(100vh - var(--bar-h) - 24px);
  overflow-y: auto;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 14px;
  box-shadow: 0 16px 40px rgba(28, 36, 48, .18);
  padding: 16px 18px 20px;
  font-family: var(--font-ui);
  font-size: 14px;
}

.panel-head { display: flex; align-items: baseline; justify-content: space-between; gap: 10px; }
.panel-head h2 { margin: 0 0 6px; font-family: var(--font-ui); font-size: 15px; }
.panel-head h2 span { font-family: var(--font-zh); font-size: 12px; font-weight: 400; color: var(--ink-faint); margin-left: 6px; }
.panel-x { border: none; background: transparent; font-size: 15px; color: var(--ink-faint); cursor: pointer; padding: 2px 4px; }

.panel .row { padding: 12px 0; border-top: 1px solid var(--line); }
.panel .row label { display: block; font-size: 12px; font-weight: 600; color: var(--ink-soft); margin-bottom: 5px; }
.panel select { width: 100%; font-family: var(--font-ui); font-size: 13px; padding: 6px 8px; border: 1px solid var(--line); border-radius: 7px; background: var(--paper); }
.row-note { margin: 6px 0 0; font-size: 11.5px; line-height: 1.45; color: var(--ink-faint); }

.row-check { display: flex; align-items: center; gap: 9px; padding: 6px 0 12px; cursor: pointer; }
.row-check span { font-size: 13.5px; }
.row-check em { font-family: var(--font-zh); font-style: normal; font-size: 12px; color: var(--ink-faint); margin-left: 6px; }

.panel-btn {
  width: 100%;
  font-family: var(--font-ui);
  font-size: 13px;
  color: #fff;
  background: var(--navy);
  border: 1px solid var(--navy);
  border-radius: 8px;
  padding: 8px 12px;
  cursor: pointer;
}
.panel-btn:hover { filter: brightness(1.12); }
.panel-btn-quiet { color: var(--ink-soft); background: transparent; border-color: var(--line); }
.panel-btn-quiet:hover { background: var(--paper); filter: none; }

.panel-clock {
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  color: var(--navy);
  margin-left: 6px;
}

/* ---------------- print ----------------

   The handout: every answer filled, every explanation open, and everything
   that needs a mouse gone. */

@media print {
  .bar, #nav, .nav-scrim, .panel, .say, .zh-chip, .reveal, .tally, .hint,
  .fcard-to { display: none !important; }
  body { font-size: 11pt; background: #fff; }
  .shell { display: block; padding: 0; }
  main { max-width: none; }
  .zh, .f-egs, .fcard-back, .why { display: block !important; }
  .td-zh::after { display: none; }
  .step { break-before: page; padding-top: 0; }
  .fcards, .chip-list { grid-template-columns: repeat(2, 1fr); }
  .q, .fcard, .pchip, .note, .formula, .goals, .letter, .tier,
  .table-wrap { break-inside: avoid; }
  .opts { display: flex; flex-wrap: wrap; gap: 6px; }
  .opt.out, .q.solved .opt:not(.right) { opacity: 1; }
  .slot { min-width: 8rem; }
}

/* ---------------- 站尾 / site footer ----------------

   同一段樣式複製到每一頁。各頁的色票變數名稱不一樣（兒童頁沒有 --ink-faint、
   成人頁沒有 --blue），所以每個顏色都串一條 fallback，缺哪一個都還是看得到。

   標誌是全站唯一的共用圖檔，放在 public/logo.png，子頁用 ../logo.png 取用。
   它本身就是連結，所以要把文字連結那條底線和左邊距擋掉——文字連結的樣式因此
   收窄成 .site-foot p a，不再套用到整個站尾裡的每個 a。 */

.site-foot {
  max-width: 46rem;
  margin: 0 auto;
  padding: 26px 20px 40px;
  border-top: 1px solid var(--line, #e3e0d8);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-wrap: wrap;
  gap: 6px 14px;
  /* 換行之後（手機）文字會落到標誌下面一整行，置中才不會左右不對稱。 */
  text-align: center;
  font-family: var(--font-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", system-ui, sans-serif);
  font-size: .8rem;
  line-height: 1.7;
  color: var(--ink-faint, var(--ink-soft, #7a8290));
}
.site-foot p { margin: 0; }

.site-foot .site-mark {
  flex: none;
  margin: 0;
  padding: 0;
  border: 0;
  line-height: 0;
  border-radius: 50%;
  transition: opacity .12s;
}
.site-foot .site-mark img { display: block; width: 34px; height: 34px; }
.site-foot .site-mark:hover { opacity: .78; }

.site-foot p a {
  margin-left: 7px;
  padding-bottom: 1px;
  color: var(--navy, var(--blue, #1d3f6e));
  font-weight: 600;
  text-decoration: none;
  border-bottom: 1px solid currentColor;
}
.site-foot p a:hover { opacity: .7; }

@media print { .site-foot { display: none; } }