:root {
  --bg: #f8f5ec; --card: #ffffff; --ink: #22302c; --muted: #66746f; --line: #e0d9c6; --soft: #f1ecdf;
  --acc: #0f8b6c; --acc2: #c2452d; --ok: #1f9d55; --no: #d64545; --okbg: #e3f6ea; --nobg: #fde8e8;
  --b1: #f0a531; --b2: #3fb27f; --b3: #3f8fd8; --b4: #b04a7c;
  --shadow: 0 2px 0 rgba(36, 48, 74, .08), 0 6px 18px rgba(36, 48, 74, .06);
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #161a24; --card: #202634; --ink: #e9edf5; --muted: #9aa3b5; --line: #343c4e; --soft: #2a3142;
    --acc: #3cc79f; --acc2: #ff8a6b; --ok: #4cc884; --no: #ff7070; --okbg: #1d3a2a; --nobg: #43242a; --shadow: none;
  }
}
:root[data-theme="dark"] {
  --bg: #161a24; --card: #202634; --ink: #e9edf5; --muted: #9aa3b5; --line: #343c4e; --soft: #2a3142;
  --acc: #3cc79f; --acc2: #ff8a6b; --ok: #4cc884; --no: #ff7070; --okbg: #1d3a2a; --nobg: #43242a; --shadow: none;
}
* { box-sizing: border-box; }
:root { --kai: "BiauKai", "DFKai-SB", "標楷體", "Kaiti TC", "STKaiti", "Noto Serif TC", "PMingLiU", serif; }
[hidden] { display: none !important; }
html, body { margin: 0; }
body {
  background: var(--bg); color: var(--ink); line-height: 1.6;
  font: 17px/1.6 system-ui, -apple-system, "Segoe UI", "PingFang TC", "Microsoft JhengHei", "Noto Sans TC", sans-serif;
}
a { color: var(--acc2); text-decoration: none; }
button { font: inherit; color: inherit; cursor: pointer; }
h1 { font-size: 1.6rem; line-height: 1.3; margin: .2em 0; }

.top { display: flex; align-items: center; justify-content: space-between; gap: 12px; flex-wrap: wrap; padding: 10px 16px; border-bottom: 1px solid var(--line); background: var(--card); position: sticky; top: 0; z-index: 5; }
.brand { display: flex; align-items: center; gap: 10px; color: var(--ink); }
.logo { width: 42px; height: 42px; display: grid; place-items: center; border-radius: 11px; background: var(--acc); color: #fff; font: 700 1.6rem/1 var(--kai); }
.bt b { display: block; font-size: 1.15rem; }
.bt small { color: var(--muted); font-size: .78rem; }
.tools { display: flex; gap: 8px; align-items: center; }
select, .pill { border: 1px solid var(--line); background: var(--soft); color: var(--ink); border-radius: 999px; padding: 6px 12px; font: inherit; font-size: .9rem; }
main { max-width: 980px; margin: 0 auto; padding: 16px; overflow-wrap: anywhere; }
.card, .topic, .sheet, .rv { min-width: 0; overflow-x: auto; }
.foot { max-width: 980px; margin: 24px auto; padding: 0 16px 24px; color: var(--muted); font-size: .85rem; text-align: center; }

.hero p { color: var(--muted); margin-top: 0; }
.grades { display: grid; grid-template-columns: repeat(auto-fill, minmax(150px, 1fr)); gap: 12px; }
.gcard { display: flex; flex-direction: column; gap: 2px; padding: 14px; border-radius: 16px; background: var(--card); color: var(--ink); box-shadow: var(--shadow); border: 1px solid var(--line); border-top: 6px solid var(--band); transition: transform .12s; }
.gcard:hover { transform: translateY(-2px); }
.gcard.b1 { --band: var(--b1); } .gcard.b2 { --band: var(--b2); } .gcard.b3 { --band: var(--b3); } .gcard.b4 { --band: var(--b4); }
.gn { font-size: 2.2rem; font-weight: 800; color: var(--band); line-height: 1; }
.gl { font-weight: 700; }
.gc { color: var(--muted); font-size: .85rem; }
.bar { height: 6px; background: var(--soft); border-radius: 3px; overflow: hidden; margin-top: 6px; }
.bar i { display: block; height: 100%; background: var(--band); }

.crumb { display: flex; gap: 10px; align-items: center; margin-bottom: 6px; flex-wrap: wrap; }
.ghead, .phead { margin-bottom: 14px; }
.cur-tag { color: var(--muted); font-size: .9rem; }
.acts { display: flex; gap: 10px; flex-wrap: wrap; margin-top: 10px; }
.btn { display: inline-flex; align-items: center; gap: 6px; border: 0; border-radius: 12px; padding: 9px 16px; background: var(--acc); color: #fff; font-weight: 700; box-shadow: 0 3px 0 rgba(0, 0, 0, .15); }
.btn:active { transform: translateY(2px); box-shadow: none; }
.btn.big { padding: 12px 22px; font-size: 1.05rem; }
.btn.ghost { background: var(--soft); color: var(--ink); border: 1px solid var(--line); box-shadow: none; }
.btn:disabled { opacity: .5; }
.link { background: none; border: 0; color: var(--acc2); padding: 0; font-size: .95rem; }
.empty { color: var(--muted); }

.topics { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 10px; }
.topic { display: grid; grid-template-columns: 1fr auto; gap: 4px 8px; padding: 12px 14px; border-radius: 14px; background: var(--card); color: var(--ink); border: 1px solid var(--line); box-shadow: var(--shadow); }
.topic:hover { border-color: var(--acc); }
.tn { font-weight: 700; }
.tags { grid-column: 1 / -1; display: flex; flex-wrap: wrap; gap: 4px; }
.tag { font-size: .72rem; padding: 1px 8px; border-radius: 999px; background: var(--soft); color: var(--muted); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; max-width: 100%; }
.tag.t-us { color: #2f6fde; } .tag.t-tw { color: #1f9d55; } .tag.t-aops { color: #c0392b; }
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) .tag.t-us { color: #7fb0ff; } :root:not([data-theme="light"]) .tag.t-tw { color: #6fdc9b; } :root:not([data-theme="light"]) .tag.t-aops { color: #ff8f80; } }
.ts { grid-column: 1 / -1; color: var(--muted); font-size: .82rem; }
.stars { color: #f5b400; letter-spacing: 1px; }
.stars i { color: var(--line); font-style: normal; }

.score { display: flex; gap: 16px; align-items: center; flex-wrap: wrap; color: var(--muted); font-size: .92rem; margin-bottom: 8px; }
.score .link { margin-left: auto; }
.card { background: var(--card); border: 1px solid var(--line); border-radius: 18px; padding: 20px; box-shadow: var(--shadow); }
.q { font-size: 1.2rem; line-height: 1.9; overflow-wrap: anywhere; }
.figs { margin: 10px 0; display: flex; gap: 12px; flex-wrap: wrap; align-items: center; }
.fig { max-width: 100%; height: auto; }
.dots { font-size: 1.7rem; line-height: 1.3; display: flex; gap: 22px; flex-wrap: wrap; }
.dots .grp { display: inline-block; }
.choices { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 10px; margin-top: 14px; }
.ch { display: flex; gap: 10px; align-items: center; text-align: left; padding: 12px 14px; border-radius: 12px; border: 2px solid var(--line); background: var(--soft); font-size: 1.08rem; }
.ch b { flex: none; width: 28px; height: 28px; display: grid; place-items: center; border-radius: 50%; background: var(--card); font-size: .9rem; }
.ch:hover:not(:disabled) { border-color: var(--acc2); }
.ch.right { border-color: var(--ok); background: var(--okbg); }
.ch.wrong { border-color: var(--no); background: var(--nobg); }
.ch:disabled { cursor: default; }
.ansrow { display: flex; gap: 10px; margin-top: 16px; }
.ansrow input { flex: 1; min-width: 0; font: inherit; font-size: 1.3rem; padding: 10px 14px; border-radius: 12px; border: 2px solid var(--line); background: var(--bg); color: var(--ink); }
.ansrow input:focus { outline: none; border-color: var(--acc2); }
.keys { display: flex; flex-wrap: wrap; gap: 6px; margin-top: 8px; align-items: center; }
.key { min-width: 40px; padding: 5px 10px; border-radius: 9px; border: 1px solid var(--line); background: var(--soft); font-size: 1.05rem; }
.fmt { color: var(--muted); font-size: .78rem; margin-left: 4px; }
.fb { margin-top: 12px; font-weight: 700; min-height: 1.4em; }
.fb.ok { color: var(--ok); } .fb.no { color: var(--no); }
.fb .h { display: block; font-weight: 400; color: var(--ink); margin-top: 4px; }
.sol { margin-top: 14px; padding: 14px 16px; border-radius: 14px; background: var(--soft); }
.sol h3 { margin: 0 0 6px; font-size: 1.05rem; }
.sol ol, .steps { margin: 0; padding-left: 1.4em; line-height: 1.9; }
.sol li, .steps li { margin: 4px 0; }
.ansline { margin: 10px 0 0; }
.sol.fold ol, .sol.fold .ansline { display: none; }
.sol.fold h3::after { content: " ▸"; }
.sol.fold h3 { cursor: pointer; color: var(--acc2); }
.next { margin: 14px 0; text-align: right; }

.qprog { display: flex; gap: 6px; align-items: center; flex-wrap: wrap; margin-bottom: 10px; color: var(--muted); font-size: .9rem; }
.qprog i { width: 22px; height: 8px; border-radius: 4px; background: var(--line); }
.qprog i.ok { background: var(--ok); } .qprog i.no { background: var(--no); } .qprog i.now { background: var(--acc); }
.qprog span { margin-left: 8px; }
.result { text-align: center; padding: 10px 0 20px; }
.result .acts { justify-content: center; }
.big-score { font-size: 4rem; font-weight: 800; color: var(--acc); line-height: 1; }
.big-score small { font-size: 1.6rem; color: var(--muted); }
.rv { background: var(--card); border: 1px solid var(--line); border-left: 6px solid var(--ok); border-radius: 12px; padding: 10px 14px; margin: 8px 0; }
.rv.no { border-left-color: var(--no); }
.rv summary { cursor: pointer; }
.rv .q { font-size: 1.05rem; margin-top: 8px; }

/* math pieces */
.fr { display: inline-flex; flex-direction: column; vertical-align: middle; text-align: center; font-size: .9em; line-height: 1.15; margin: 0 .12em; }
.fr > span:first-child { border-bottom: 1.5px solid currentColor; padding: 0 .2em; }
.fr > span:last-child { padding: 0 .2em; }
.rt { border-top: 1.5px solid currentColor; padding: 0 .1em; margin-left: .05em; }
sup { font-size: .7em; }

/* svg classes */
.f-soft { fill: var(--soft); stroke: var(--ink); stroke-width: 1.5; }
.f-line { stroke: var(--ink); fill: none; }
.f-acc { stroke: var(--acc); fill: none; }
.f-accfill { fill: var(--acc); stroke: var(--ink); stroke-width: 1; }
.f-dot { fill: var(--ink); }
.f-txt { fill: var(--ink); font-family: inherit; }
.f-acctxt { fill: var(--acc); font-family: inherit; }
.f-grid { stroke: var(--line); stroke-width: 1; }

/* worksheet */
.sheet { background: var(--card); border: 1px solid var(--line); border-radius: 14px; padding: 20px; margin: 12px 0; }
.sheet h1 { font-size: 1.3rem; }
.who { color: var(--muted); }
.pqs { padding-left: 1.6em; }
.pq { margin: 14px 0; break-inside: avoid; }
.pq .q { font-size: 1.05rem; }
.pch { display: flex; flex-wrap: wrap; gap: 6px 22px; margin-top: 4px; }
.line { border-bottom: 1px solid var(--muted); width: 220px; height: 30px; }
.keys-list > li { margin: 10px 0; break-inside: avoid; }
.keys-list .steps { font-size: .9rem; color: var(--muted); }

@media (max-width: 560px) {
  body { font-size: 16px; }
  .q { font-size: 1.1rem; }
  .bt small { display: none; }
  .grades { grid-template-columns: repeat(2, 1fr); }
  .topics { grid-template-columns: 1fr; }
  .card { padding: 14px; }
  .top { padding: 8px 12px; }
  .tools select { max-width: 150px; }
  .qprog span { flex-basis: 100%; margin: 4px 0 0; }
}
@media print {
  .top, .foot, .noprint { display: none !important; }
  body { background: #fff; color: #000; }
  main { padding: 0; max-width: none; }
  .sheet { border: 0; padding: 0; }
  .sheet.key { break-before: page; }
  :root { --ink: #000; --soft: #f2f2f2; --acc: #333; --line: #bbb; --muted: #555; --card: #fff; }
}

/* ---- writing ---- */
.sec { font-size: 1.15rem; margin: 22px 0 8px; }
.muted { color: var(--muted); font-size: .92rem; }
.en2 { color: var(--muted); font-size: .9rem; margin: 4px 0 0; }
.gtag { color: var(--muted); font-size: .8rem; align-self: center; }
.topic.task { border-left: 5px solid var(--acc2); }
.snip { grid-column: 1 / -1; color: var(--muted); font-size: .82rem; font-family: var(--kai); }
.lesson { background: var(--card); border: 1px solid var(--line); border-radius: 14px; padding: 10px 16px; margin-bottom: 12px; }
.lesson summary { cursor: pointer; font-weight: 700; }
.lesson .ex { margin: 6px 0 4px; padding-left: 1.3em; font-family: var(--kai); }
.lesson u { text-decoration-color: var(--acc); text-decoration-thickness: 2px; }
.lesson b, .sol b { color: var(--acc); }
.passage { margin: 10px 0; padding: 12px 16px; border-left: 4px solid var(--acc2); background: var(--soft); border-radius: 8px; font-family: var(--kai); font-size: 1.1rem; line-height: 1.8; }
.q { font-family: inherit; }
.tapline { margin: 16px 0 10px; display: flex; flex-wrap: wrap; gap: 8px; font-family: var(--kai); font-size: 1.3rem; }
.tw { border: 2px solid var(--line); background: var(--soft); border-radius: 10px; padding: 4px 10px; font-family: inherit; }
.tw.sel { border-color: var(--acc2); background: color-mix(in srgb, var(--acc2) 18%, var(--card)); }
.tw.right { border-color: var(--ok); background: var(--okbg); }
.tw.wrong { border-color: var(--no); background: var(--nobg); text-decoration: line-through; }
.ordpool { display: flex; flex-direction: column; gap: 8px; margin: 14px 0 8px; }
.oi { display: flex; gap: 10px; align-items: flex-start; text-align: left; padding: 10px 12px; border-radius: 12px; border: 2px solid var(--line); background: var(--soft); font-family: var(--kai); font-size: 1.05rem; }
.oi b { flex: none; width: 28px; height: 28px; border-radius: 50%; display: grid; place-items: center; background: var(--card); border: 1px dashed var(--muted); font-family: system-ui, sans-serif; font-size: .9rem; }
.oi.sel { border-color: var(--acc2); }
.oi.sel b { background: var(--acc2); color: #fff; border: 0; }
.oi.done { border-color: var(--ok); background: var(--okbg); }
.oi.done b { background: var(--ok); color: #fff; border: 0; }
.row { display: flex; gap: 10px; margin-top: 12px; flex-wrap: wrap; align-items: center; }
.row.between { justify-content: space-between; }
.ansrow input { font-family: var(--kai); }

.prompt .q { font-size: 1.15rem; }
.topicpick, .starters { display: flex; flex-wrap: wrap; gap: 6px; align-items: center; margin-top: 10px; }
.topicpick span, .starters span { color: var(--muted); font-size: .85rem; margin-right: 4px; }
.chip { border: 1px solid var(--line); background: var(--soft); border-radius: 999px; padding: 3px 12px; font-size: .9rem; }
.chip.on { background: var(--acc2); color: #fff; border-color: var(--acc2); }
.chip.v { font-style: italic; }
.stepper { display: flex; gap: 6px; margin: 14px 0 10px; flex-wrap: wrap; }
.stp { flex: 1; min-width: 90px; border: 2px solid var(--line); background: var(--card); border-radius: 12px; padding: 8px; font-weight: 700; color: var(--muted); }
.stp.on { border-color: var(--acc); color: var(--acc); }
.plan { display: block; margin: 12px 0; }
.pl { font-weight: 700; display: block; }
.ph { color: var(--muted); font-size: .85rem; display: block; font-family: var(--kai); }
textarea { width: 100%; font: inherit; border: 2px solid var(--line); border-radius: 12px; padding: 10px 12px; background: var(--bg); color: var(--ink); resize: vertical; }
textarea:focus { outline: none; border-color: var(--acc2); }
.draft { min-height: 340px; margin-top: 12px; font-family: var(--kai); font-size: 1.1rem; line-height: 1.8; }
.wc { color: var(--muted); }
.wc .lo { color: var(--acc); } .wc .hi { color: var(--no); } .wc .okc { color: var(--ok); }
.statrow { display: flex; gap: 18px; flex-wrap: wrap; color: var(--muted); }
.statrow b { color: var(--ink); font-size: 1.2rem; }
.card h3 { font-size: 1.05rem; margin: 18px 0 6px; }
.notes { list-style: none; padding: 0; margin: 0; }
.notes li { padding: 7px 10px; border-radius: 10px; margin: 5px 0; background: var(--soft); }
.notes li.fix { background: var(--nobg); } .notes li.good { background: var(--okbg); }
.marked { padding: 12px 16px; border-radius: 12px; border: 1px solid var(--line); font-family: var(--kai); line-height: 1.9; }
mark.fix { background: color-mix(in srgb, var(--no) 30%, transparent); color: inherit; border-radius: 3px; }
mark.tip { background: color-mix(in srgb, #f5b400 35%, transparent); color: inherit; border-radius: 3px; }
.checks label { display: flex; gap: 8px; align-items: flex-start; margin: 6px 0; }
.checks input { margin-top: 6px; width: 18px; height: 18px; }
.mentor { padding: 6px 20px 10px; border-radius: 12px; background: var(--soft); font-family: var(--kai); font-size: 1.08rem; line-height: 1.85; }
.mentor h3 { text-align: center; font-family: inherit; }
.note { margin-top: 12px; padding: 10px 14px; border-radius: 12px; border: 1px dashed var(--acc); }
.pord { list-style: none; padding-left: 0; font-family: var(--kai); }
.pord li { margin: 4px 0; }

/* ---- Chinese Dojo ---- */
.gs { color: var(--muted); font-size: .78rem; }
.uicon { display: inline-grid; place-items: center; width: 1.7em; height: 1.7em; border-radius: 8px; background: var(--acc); color: #fff; font: 700 .95rem/1 var(--kai); margin-right: 4px; vertical-align: 2px; }
.cur-tag { font-weight: 400; }
.q { font-size: 1.15rem; }
.passage { font-size: 1.15rem; line-height: 1.95; }
.tapline { gap: 4px; font-family: var(--kai); font-size: 1.45rem; }
.tw { padding: 2px 6px; min-width: 40px; min-height: 44px; border-radius: 8px; font-family: inherit; }
.tp { display: inline-grid; place-items: center; min-height: 44px; padding: 0 2px; color: var(--muted); }
.choices.tight { grid-template-columns: repeat(auto-fit, minmax(120px, 1fr)); }
.choices.tight .ch { font-size: 1.3rem; justify-content: flex-start; }
.ch span { font-family: inherit; }
.ordout { min-height: 2.4em; margin: 12px 0 0; padding: 8px 12px; border-radius: 10px; border: 2px dashed var(--line); font-family: var(--kai); font-size: 1.3rem; }
.ordout.ph { color: var(--muted); font-size: .95rem; font-family: inherit; }
.ordout.done { border-style: solid; border-color: var(--ok); background: var(--okbg); }
.ordpool.chips { flex-direction: row; flex-wrap: wrap; }
.ordpool.chips .oi { align-items: center; font-size: 1.2rem; }
.pics { display: flex; flex-wrap: wrap; align-items: center; gap: 6px; margin: 12px 0 4px; }
.pic { position: relative; display: grid; place-items: center; width: 68px; height: 68px; border-radius: 14px; background: var(--soft); border: 1px solid var(--line); font-size: 2.2rem; }
.pic i { position: absolute; top: 2px; left: 6px; font-size: .7rem; font-style: normal; color: var(--muted); }
.arr { color: var(--muted); }
.mentor p { text-indent: 2em; margin: .35em 0; }
.mentor p.pl0, .mentor.poem p { text-indent: 0; }
.mentor.poem { text-align: center; }
.mwc { color: var(--muted); font-family: system-ui, sans-serif; font-size: .8rem; text-align: right; }
.draft { font-size: 1.15rem; line-height: 1.9; }
.chip.pu { min-width: 36px; font-size: 1rem; }
.marked { white-space: normal; }
.lesson .ex { font-size: 1.05rem; }