:root {
  --bg: #f7f4ee;
  --surface: #ffffff;
  --ink: #1f2a30;
  --muted: #64717a;
  --line: #e3ddd2;
  --teal: #0d6e75;
  --teal-2: #138d95;
  --teal-soft: #dff1f0;
  --saffron: #f4a73b;
  --saffron-dark: #c97d13;
  --lotus: #e2557a;
  --lotus-soft: #fde4ea;
  --good: #2e9b5f;
  --good-soft: #def4e7;
  --bad: #d2463a;
  --bad-soft: #fde3e0;
  --locked: #c9c3b8;
  --locked-edge: #a39c90;
  --shadow: 0 3px 0 rgba(31, 42, 48, .12);
  --radius: 16px;
  --km: "Noto Sans Khmer", "Khmer OS", "Leelawadee UI", sans-serif;
  --ui: "Nunito", system-ui, -apple-system, "Segoe UI", sans-serif;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #141b1f; --surface: #1d272c; --ink: #eef2f3; --muted: #9aa8b0; --line: #2d3a40;
    --teal: #2fb3ba; --teal-2: #4cc7cd; --teal-soft: #173538; --saffron: #f6b456; --saffron-dark: #d99327;
    --lotus: #f07b98; --lotus-soft: #3a2229; --good: #4cc483; --good-soft: #193526; --bad: #f0786c; --bad-soft: #3c2220;
    --locked: #3e4b52; --locked-edge: #2c363b; --shadow: 0 3px 0 rgba(0, 0, 0, .35); color-scheme: dark;
  }
}
:root[data-theme="dark"] {
    --bg: #141b1f; --surface: #1d272c; --ink: #eef2f3; --muted: #9aa8b0; --line: #2d3a40;
    --teal: #2fb3ba; --teal-2: #4cc7cd; --teal-soft: #173538; --saffron: #f6b456; --saffron-dark: #d99327;
    --lotus: #f07b98; --lotus-soft: #3a2229; --good: #4cc483; --good-soft: #193526; --bad: #f0786c; --bad-soft: #3c2220;
    --locked: #3e4b52; --locked-edge: #2c363b; --shadow: 0 3px 0 rgba(0, 0, 0, .35); color-scheme: dark;
}
* { box-sizing: border-box; }
html, body { margin: 0; }
body {
  background: var(--bg); color: var(--ink); font: 500 16px/1.45 var(--ui);
  min-height: 100dvh; display: flex; flex-direction: column;
  padding-bottom: calc(70px + env(safe-area-inset-bottom));
}
button { font: inherit; color: inherit; cursor: pointer; }
.km { font-family: var(--km); line-height: 1.75; font-size: 1.22em; font-weight: 500; }
.km .km { font-size: 1em; }
.rom { color: var(--muted); font-style: italic; }
.loading { text-align: center; padding: 60px 16px; color: var(--muted); }

/* top bar */
.topbar {
  position: sticky; top: 0; z-index: 5; display: flex; align-items: center; justify-content: space-between;
  padding: 10px 16px; background: var(--surface); border-bottom: 1px solid var(--line);
}
.brand { display: flex; align-items: center; gap: 8px; background: none; border: 0; padding: 0; font-weight: 900; font-size: 19px; color: var(--teal); }
.stats { display: flex; gap: 14px; font-weight: 800; }
.stat { display: inline-flex; align-items: center; gap: 4px; }
.stat.streak b { color: var(--saffron-dark); }
.stat.xp b { color: var(--teal); }

main { flex: 1; width: 100%; max-width: 720px; margin: 0 auto; padding: 18px 16px 28px; outline: none; }

/* tab bar */
.tabbar {
  position: fixed; bottom: 0; left: 0; right: 0; z-index: 5; display: flex; justify-content: center; gap: 4px;
  background: var(--surface); border-top: 1px solid var(--line); padding: 6px 8px calc(6px + env(safe-area-inset-bottom));
}
.tabbar button {
  flex: 1; max-width: 140px; min-width: 0; display: flex; flex-direction: column; align-items: center; gap: 1px;
  background: none; border: 0; border-radius: 12px; padding: 6px 4px; font-weight: 800; font-size: 12px; color: var(--muted);
}
.tabbar button span { font-size: 20px; line-height: 1.2; font-family: var(--km), var(--ui); }
.tabbar button.on { color: var(--teal); background: var(--teal-soft); }
body.in-lesson .tabbar, body.in-lesson .topbar { display: none; }
body.in-lesson { padding-bottom: 0; }

/* home path */
.hello { display: flex; align-items: center; gap: 14px; margin-bottom: 18px; }
.hello h1 { margin: 0; font-size: 22px; font-weight: 900; }
.hello p { margin: 2px 0 0; color: var(--muted); }
.goal { flex: none; width: 58px; height: 58px; }
.unit { margin: 0 0 26px; }
.unit-head {
  border-radius: var(--radius); padding: 14px 16px; color: #fff; background: var(--teal); box-shadow: var(--shadow);
  display: flex; justify-content: space-between; align-items: center; gap: 12px;
}
.unit.tone-1 .unit-head { background: #b4572c; }
.unit.tone-2 .unit-head { background: #5b5a9e; }
.unit.tone-3 .unit-head { background: #2f7a4f; }
.goal { flex: none; display: block; }
.unit-head h2 { margin: 0; font-size: 18px; font-weight: 900; }
.unit-head p { margin: 2px 0 0; opacity: .9; font-size: 14px; }
.unit-head .unit-km { font-size: 26px; white-space: nowrap; }
.path { display: flex; flex-direction: column; align-items: center; gap: 14px; padding: 18px 0 4px; }
.node { display: flex; flex-direction: column; align-items: center; gap: 4px; background: none; border: 0; padding: 0; }
.node { transform: translateX(var(--wiggle, 0)); }
.node .disc {
  width: 66px; height: 62px; border-radius: 50%; display: grid; place-items: center; font-size: 26px;
  background: var(--teal-2); color: #fff; box-shadow: 0 6px 0 var(--teal); transition: transform .08s;
}
.node:active .disc { transform: translateY(4px); box-shadow: 0 2px 0 var(--teal); }
.node.done .disc { background: var(--saffron); box-shadow: 0 6px 0 var(--saffron-dark); }
.node.locked .disc { background: var(--locked); box-shadow: 0 6px 0 var(--locked-edge); color: #fff; cursor: not-allowed; }
.node .label { font-weight: 800; font-size: 13px; max-width: 150px; text-align: center; }
.node.locked .label { color: var(--muted); }
.node.current .disc { outline: 4px solid var(--saffron); outline-offset: 4px; }

/* cards & buttons */
.card { background: var(--surface); border: 2px solid var(--line); border-radius: var(--radius); padding: 16px; }
.btn {
  display: inline-flex; justify-content: center; align-items: center; gap: 8px; border: 0; border-radius: 14px;
  padding: 13px 20px; font-weight: 900; font-size: 16px; letter-spacing: .02em; text-transform: uppercase;
  background: var(--teal-2); color: #fff; box-shadow: 0 4px 0 var(--teal);
}
.btn:active { transform: translateY(3px); box-shadow: 0 1px 0 var(--teal); }
.btn[disabled] { background: var(--locked); box-shadow: 0 4px 0 var(--locked-edge); cursor: not-allowed; }
.btn.ghost { background: var(--surface); color: var(--teal); box-shadow: 0 4px 0 var(--line); border: 2px solid var(--line); }
.btn.wide { width: 100%; }

/* lesson screen */
.lesson { display: flex; flex-direction: column; min-height: calc(100dvh - 36px); }
.lesson-top { display: flex; align-items: center; gap: 12px; margin-bottom: 18px; }
.quit { background: none; border: 0; font-size: 26px; line-height: 1; color: var(--muted); padding: 4px; }
.bar { flex: 1; height: 16px; border-radius: 99px; background: var(--line); overflow: hidden; }
.bar > i { display: block; height: 100%; background: var(--saffron); border-radius: 99px; transition: width .3s; }
.hearts { font-weight: 900; color: var(--lotus); white-space: nowrap; }
.prompt-label { font-weight: 900; font-size: 20px; margin: 4px 0 14px; }
.prompt { display: flex; align-items: center; gap: 12px; margin-bottom: 18px; flex-wrap: wrap; }
.prompt .big { font-size: 34px; font-weight: 700; }
.prompt .big.km { font-size: 52px; line-height: 1.6; }
.prompt .en-big { font-size: 26px; font-weight: 800; }
.speak { border: 2px solid var(--line); background: var(--surface); border-radius: 12px; width: 44px; height: 44px; font-size: 20px; flex: none; }
.choices { display: grid; gap: 10px; }
.choices.two { grid-template-columns: 1fr 1fr; }
.choice {
  text-align: left; border: 2px solid var(--line); border-bottom-width: 4px; border-radius: 14px; background: var(--surface);
  padding: 12px 14px; font-weight: 700; font-size: 17px; min-height: 54px;
}
.choice .km { font-size: 30px; line-height: 1.6; }
.choices.glyphs .choice { text-align: center; }
.choice .km.glyph { font-size: 52px; line-height: 1.5; }
.choice .num { font-size: 26px; }
.choice.sel { border-color: var(--teal-2); background: var(--teal-soft); }
.choice.right { border-color: var(--good); background: var(--good-soft); }
.choice.wrong { border-color: var(--bad); background: var(--bad-soft); }
.choice.faded { opacity: .45; }
.choice:disabled { cursor: default; }
.letter-big { font-family: var(--km); font-size: 110px; line-height: 1.35; text-align: center; margin: 0 0 6px; }

/* match */
.match { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
.match .col { display: grid; gap: 10px; align-content: start; }
.tile {
  border: 2px solid var(--line); border-bottom-width: 4px; border-radius: 12px; background: var(--surface);
  padding: 10px 12px; font-weight: 700; min-height: 54px;
}
.tile .km { font-size: 28px; }
.tile.sel { border-color: var(--teal-2); background: var(--teal-soft); }
.tile.ok { border-color: var(--line); color: var(--muted); opacity: .4; cursor: default; }
.tile.miss { border-color: var(--bad); background: var(--bad-soft); }

/* sentence builder */
.answer-line { min-height: 70px; border-bottom: 2px solid var(--line); display: flex; flex-wrap: wrap; gap: 8px; padding: 6px 0 10px; margin-bottom: 18px; }
.bank { display: flex; flex-wrap: wrap; gap: 8px; justify-content: center; }
.word {
  border: 2px solid var(--line); border-bottom-width: 4px; border-radius: 12px; background: var(--surface); padding: 6px 12px;
  display: inline-flex; flex-direction: column; align-items: center; line-height: 1.2;
}
.word .km { font-size: 30px; line-height: 1.95; }
.word small { color: var(--muted); font-style: italic; font-size: 12px; }
.word.used { visibility: hidden; }

/* feedback sheet */
.spacer { flex: 1; min-height: 18px; }
.check-row { position: sticky; bottom: 0; padding: 14px 0 calc(14px + env(safe-area-inset-bottom)); background: var(--bg); }
.sheet { border-radius: var(--radius); padding: 14px 16px; margin-bottom: 12px; }
.sheet.ok { background: var(--good-soft); color: var(--good); }
.sheet.no { background: var(--bad-soft); color: var(--bad); }
.sheet h3 { margin: 0 0 4px; font-size: 19px; font-weight: 900; }
.sheet p { margin: 0; color: var(--ink); }
.sheet .km { font-size: 26px; }
.sheet + .btn.ok-btn { background: var(--good); box-shadow: 0 4px 0 #1f6e42; }
.sheet.no + .btn { background: var(--bad); box-shadow: 0 4px 0 #9c2c22; }
.tip { margin: 0 0 14px; padding: 10px 12px; border-left: 4px solid var(--saffron); background: var(--surface); border-radius: 8px; color: var(--muted); font-size: 14px; }

/* results */
.results { text-align: center; padding-top: 40px; }
.results .burst { font-size: 64px; }
.results h1 { font-weight: 900; margin: 6px 0; }
.result-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; margin: 22px 0; }
.result-grid .card { padding: 12px 8px; }
.result-grid b { display: block; font-size: 24px; font-weight: 900; }
.result-grid span { color: var(--muted); font-size: 13px; font-weight: 800; text-transform: uppercase; }

/* script reference */
.section-title { font-size: 22px; font-weight: 900; margin: 6px 0 4px; }
.lead { color: var(--muted); margin: 0 0 14px; }
.grid-letters { display: grid; grid-template-columns: repeat(auto-fill, minmax(78px, 1fr)); gap: 8px; margin-bottom: 22px; }
.lt { border: 2px solid var(--line); border-radius: 12px; background: var(--surface); text-align: center; padding: 6px 4px; }
.lt .km { font-size: 40px; line-height: 1.5; display: block; }
.lt .km.subform { font-size: 30px; line-height: 1.3; color: var(--muted); min-height: 1em; }
.lt small { display: block; font-size: 12px; color: var(--muted); }
.lt .ser { display: inline-block; font-size: 11px; font-weight: 900; border-radius: 6px; padding: 0 6px; margin-top: 2px; }
.ser.a { background: var(--teal-soft); color: var(--teal); }
.ser.o { background: var(--lotus-soft); color: var(--lotus); }
.legend { display: flex; gap: 10px; flex-wrap: wrap; margin-bottom: 10px; font-size: 14px; }
table.vtab { width: 100%; border-collapse: collapse; background: var(--surface); border-radius: 12px; overflow: hidden; margin-bottom: 22px; font-size: 15px; }
.vtab th, .vtab td { padding: 8px 10px; border-bottom: 1px solid var(--line); text-align: left; }
.vtab th { font-size: 12px; text-transform: uppercase; color: var(--muted); }
.vtab td.km { font-size: 32px; }
.table-wrap { overflow-x: auto; }

/* about */
.prose h2 { font-size: 20px; font-weight: 900; margin: 22px 0 6px; }
.prose p, .prose li { color: var(--ink); }
.prose a { color: var(--teal); }
.prose code { background: var(--surface); border: 1px solid var(--line); border-radius: 6px; padding: 0 4px; }
.review-empty { text-align: center; padding: 40px 10px; color: var(--muted); }
.row-actions { display: flex; gap: 10px; flex-wrap: wrap; margin-top: 16px; }
.toast { position: fixed; left: 50%; bottom: 90px; transform: translateX(-50%); background: var(--ink); color: var(--bg); padding: 8px 14px; border-radius: 10px; font-weight: 800; font-size: 14px; z-index: 20; }

@media (max-width: 420px) {
  .prompt .big.km { font-size: 44px; }
  .choice .km, .tile .km { font-size: 26px; }
  .letter-big { font-size: 96px; }
  .node { transform: translateX(calc(var(--wiggle, 0px) * .7)); }
}
@media (prefers-reduced-motion: reduce) { * { transition: none !important; } }

/* ---------- v2: on-ramp, peek, hints, letters, flashcards ---------- */
.hello-rom { font-size: 16px; }
.eyebrow { margin: 0 0 2px; font-size: 12px; font-weight: 900; letter-spacing: .08em; text-transform: uppercase; opacity: .85; }
.unit-side { display: flex; flex-direction: column; align-items: flex-end; gap: 6px; }
.chip-btn { border: 2px solid currentColor; background: transparent; border-radius: 99px; padding: 3px 12px; font-weight: 800; font-size: 13px; color: inherit; }
.unit-head .chip-btn { color: #fff; border-color: rgba(255,255,255,.7); }
.welcome { background: var(--surface); border: 2px solid var(--line); border-radius: var(--radius); padding: 16px; margin-bottom: 22px; }
.welcome h2 { margin: 0 0 6px; font-size: 19px; font-weight: 900; }
.welcome p { margin: 0; color: var(--muted); }
.node.practice .disc { background: var(--lotus); box-shadow: 0 6px 0 #a83756; }
.node.practice.locked .disc { background: var(--locked); box-shadow: 0 6px 0 var(--locked-edge); }

.card-intro { text-align: center; display: grid; gap: 6px; justify-items: center; padding: 8px 4px 0; }
.new-badge { font-size: 12px; font-weight: 900; letter-spacing: .1em; text-transform: uppercase; color: var(--lotus); background: var(--lotus-soft); border-radius: 99px; padding: 3px 12px; }
.card-face { display: flex; align-items: center; justify-content: center; gap: 14px; flex-wrap: wrap; }
.km.huge { font-size: 66px; line-height: 1.6; }
.km.mid { font-size: 56px; line-height: 1.5; }
.letter-huge { font-family: var(--km); font-size: 128px; line-height: 1.3; margin: 0; }
.card-rom { margin: 0; font-size: 22px; font-style: italic; color: var(--teal); font-weight: 700; }
.card-en { margin: 0; font-size: 24px; font-weight: 900; }
.card-note { margin: 4px 0 0; color: var(--muted); max-width: 46ch; font-size: 15px; }
.two-up { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; width: 100%; max-width: 440px; }
.two-up > div { background: var(--surface); border: 2px solid var(--line); border-radius: 14px; padding: 10px; display: grid; gap: 2px; justify-items: center; }
.two-up small { color: var(--muted); font-size: 12px; font-weight: 800; }
.two-up b { font-size: 22px; }
.lead.center, .center { text-align: center; }
.row-actions.center { justify-content: center; }
.small { font-size: 13px; }
.muted { color: var(--muted); }

.peek-row, .hint-row { display: flex; justify-content: center; margin-top: 14px; }
.peek { background: none; border: 0; color: var(--teal); font-weight: 900; font-size: 15px; text-decoration: underline; text-underline-offset: 3px; padding: 8px; }
.sheet.peeked { background: var(--teal-soft); color: var(--teal); }
.sheet.peeked + .btn { background: var(--teal-2); }
.word.shown { cursor: default; }
.word .hint-en { display: none; font-style: normal; color: var(--teal); font-weight: 800; }
.hints .word .hint-en { display: block; }

.tap-line { display: flex; flex-wrap: wrap; gap: 4px 2px; margin: 0 0 18px; }
.tap-word { background: none; border: 0; padding: 0 2px; border-bottom: 2px dotted var(--muted); border-radius: 0; }
.tap-wrap { margin: 0 0 18px; }
.tap-wrap .tap-line { margin: 0; }
.gloss-box { min-height: 2.6em; margin: 8px 0 0; padding: 8px 12px; border-radius: 12px; background: var(--surface); border: 1px solid var(--line); color: var(--muted); }
.gloss-box b { color: var(--teal); font-style: italic; }
.gloss-box .km { font-size: 24px; color: var(--ink); }
.tap-line.big .tap-word .km { font-size: 40px; line-height: 1.6; }
.tap-word.open { border-bottom-color: var(--teal); }

.read-meter { background: var(--teal-soft); color: var(--teal); border-radius: 12px; padding: 10px 12px; margin-bottom: 18px; font-weight: 700; }
.read-meter b { font-size: 20px; }
.sub-title { font-size: 18px; font-weight: 900; margin: 22px 0 8px; }
.lead.small { font-size: 14px; }
.letter-section { margin-bottom: 8px; }
.lgroup { background: var(--surface); border: 2px solid var(--line); border-radius: var(--radius); padding: 12px 14px; margin-bottom: 12px; }
.lgroup.next { border-color: var(--saffron); }
.lgroup-head { display: flex; justify-content: space-between; align-items: flex-start; gap: 10px; }
.lgroup h3 { margin: 0; font-family: var(--ui), var(--km); font-size: 22px; font-weight: 800; line-height: 1.6; }
.lgroup .row-actions { margin-top: 10px; align-items: center; }
.glyph-row { display: flex; flex-wrap: wrap; gap: 6px; margin-top: 10px; }
.glyph-chip { display: inline-grid; justify-items: center; min-width: 50px; padding: 2px 6px 6px; border-radius: 10px; background: var(--bg); border: 1px solid var(--line); }
.glyph-chip .km { font-size: 32px; line-height: 1.5; }
.bar5 { display: block; width: 34px; height: 5px; border-radius: 9px; background: linear-gradient(90deg, var(--good) calc(var(--n) * 20%), var(--line) 0); }
.meter { display: inline-flex; gap: 3px; flex: none; margin-top: 4px; }
.meter i { width: 9px; height: 18px; border-radius: 3px; background: var(--line); }
.meter i.on { background: var(--saffron); }

.decks { display: grid; grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 10px; }
.deck { text-align: left; background: var(--surface); border: 2px solid var(--line); border-bottom-width: 4px; border-radius: 14px; padding: 12px 14px; display: grid; gap: 2px; }
.deck-title { font-weight: 900; }
.flashcard { display: grid; justify-items: center; align-content: center; gap: 8px; min-height: 300px; width: 100%; background: var(--surface);
  border: 2px solid var(--line); border-bottom-width: 6px; border-radius: 22px; padding: 18px 14px; text-align: center; }
.flashcard.flipped { border-color: var(--teal-2); }
.card-back { display: grid; gap: 4px; justify-items: center; }
.btn.danger { background: var(--bad); box-shadow: 0 4px 0 #9c2c22; }
.check-row .btn.ghost + .btn.ok-btn { flex: 1; }
.check-row:has(.btn.ghost) { display: flex; gap: 10px; }
.check-row .btn.ghost { flex: 1; }
.cloud { font-size: 18px; color: var(--teal); }
.cloud.error { color: var(--bad); }
.chart { margin-bottom: 20px; }
@media (max-width: 420px) {
  .letter-huge { font-size: 108px; }
  .km.huge { font-size: 56px; }
  .tap-line.big .tap-word .km { font-size: 34px; }
}