:root {
  --bg: #faf9f5;           /* claude warm paper */
  --bg-deep: #f0eee6;      /* claude sidebar tone */
  --panel: #ffffff;
  --ink: #1f1e1d;
  --muted: #6b6a63;
  --line: #e9e6dd;
  --accent: #d97757;       /* Claude coral */
  --accent-ink: #bd5d3e;
  --accent-soft: #f6ece6;
  --gold: #c89b3c;
  --green: #3a9c6e;
  --green-soft: #e9f3ec;
  --red: #c45c4a;
  --red-soft: #f8ebe6;
  --shadow: 0 1px 2px rgba(31, 30, 29, .04), 0 4px 16px rgba(31, 30, 29, .04);
  --radius: 14px;
  --serif: "Noto Serif", "Noto Serif TC", Georgia, "Songti TC", serif;
  font-family: "Inter", "Noto Sans TC", "Noto Sans JP", system-ui, sans-serif;
}

* { box-sizing: border-box; }
html, body { margin: 0; }
body {
  background: var(--bg);
  color: var(--ink);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}
a { color: inherit; text-decoration: none; }
em { font-style: normal; }

/* ---------- top bar ---------- */
.topbar {
  position: sticky; top: 0; z-index: 20;
  display: flex; align-items: center; justify-content: space-between;
  gap: 16px; padding: 12px 20px;
  background: rgba(250, 249, 245, .82);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--line);
}
.brand { display: flex; align-items: center; gap: 10px; font-family: var(--serif); font-weight: 600; font-size: 21px; letter-spacing: -.01em; }
.brand-mark { font-size: 24px; }
.brand-text em { color: var(--accent); font-weight: 600; }

.lang-pref { display: flex; align-items: center; gap: 10px; }
.lang-pref-label { font-size: 13px; color: var(--muted); font-weight: 700; }
.seg { display: inline-flex; background: var(--panel); border: 1px solid var(--line); border-radius: 999px; padding: 3px; gap: 2px; }
.seg button {
  border: 0; background: transparent; cursor: pointer;
  font: inherit; font-weight: 700; font-size: 13px; color: var(--muted);
  padding: 5px 12px; border-radius: 999px; transition: .15s;
}
.seg button.on { background: var(--accent); color: #fff; }

/* ---------- layout ---------- */
.app { max-width: 880px; margin: 0 auto; padding: 24px 20px 80px; }
.loading { text-align: center; color: var(--muted); padding: 80px 0; }

.foot {
  text-align: center; color: var(--muted); font-size: 13px;
  padding: 24px 20px 40px; display: flex; gap: 8px; justify-content: center; flex-wrap: wrap;
}
.foot-sep { opacity: .5; }

/* ---------- hero ---------- */
.hero { text-align: center; padding: 28px 0 34px; }
.hero h1 { font-family: var(--serif); font-size: clamp(28px, 5vw, 44px); margin: 0 0 10px; font-weight: 600; letter-spacing: -.02em; }
.hero p { color: var(--muted); font-size: 17px; margin: 0; }

.section-label { font-size: 12px; letter-spacing: .14em; text-transform: uppercase; color: var(--muted); font-weight: 700; margin: 24px 4px 12px; }

/* ---------- cards ---------- */
.lang-card {
  background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius);
  box-shadow: var(--shadow); overflow: hidden; margin-bottom: 18px;
}
.lang-head { display: flex; align-items: center; gap: 14px; padding: 18px 20px; border-bottom: 1px solid var(--line); }
.lang-flag { font-size: 34px; }
.lang-name { font-family: var(--serif); font-weight: 600; font-size: 20px; letter-spacing: -.01em; }
.lang-native { color: var(--muted); font-size: 14px; font-weight: 600; }

.unit-list { display: grid; gap: 1px; background: var(--line); }
.unit-row {
  display: flex; align-items: center; gap: 14px; padding: 16px 20px;
  background: var(--panel); cursor: pointer; transition: background .15s;
}
.unit-row:hover { background: var(--accent-soft); }
.unit-emoji { font-size: 28px; }
.unit-main { flex: 1; min-width: 0; }
.unit-title { font-weight: 800; font-size: 16px; }
.unit-meta { color: var(--muted); font-size: 13px; }
.unit-go { color: var(--accent); font-weight: 800; font-size: 22px; }

.coming { padding: 16px 20px; color: var(--muted); font-size: 14px; background: var(--panel); font-style: italic; }

/* ---------- unit view ---------- */
.back { display: inline-flex; align-items: center; gap: 6px; color: var(--muted); font-weight: 700; font-size: 14px; margin-bottom: 16px; cursor: pointer; }
.back:hover { color: var(--accent); }

.unit-hero { margin-bottom: 18px; }
.unit-hero h1 { font-family: var(--serif); font-size: clamp(24px, 4vw, 34px); margin: 0 0 8px; font-weight: 600; letter-spacing: -.02em; }
.unit-hero .fi-title { color: var(--accent-ink); font-weight: 700; font-size: 15px; margin-bottom: 10px; }
.unit-hero .intro { color: var(--muted); font-size: 15px; }

.tabs { display: inline-flex; background: var(--panel); border: 1px solid var(--line); border-radius: 999px; padding: 4px; margin: 18px 0 8px; box-shadow: var(--shadow); }
.tabs button { border: 0; background: transparent; cursor: pointer; font: inherit; font-weight: 800; font-size: 15px; color: var(--muted); padding: 8px 22px; border-radius: 999px; transition: .15s; }
.tabs button.on { background: var(--accent); color: #fff; }

/* progress bar */
.prog { display: flex; align-items: center; gap: 10px; margin: 8px 0 4px; font-size: 13px; color: var(--muted); font-weight: 700; }
.prog-track { flex: 1; height: 8px; background: var(--line); border-radius: 999px; overflow: hidden; }
.prog-fill { height: 100%; background: var(--green); border-radius: 999px; transition: width .3s; }

/* ---------- scene (teaching) ---------- */
.scene { background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius); box-shadow: var(--shadow); margin: 14px 0; overflow: hidden; }
.scene-head { display: flex; align-items: center; gap: 12px; padding: 16px 18px; cursor: pointer; }
.scene-num { width: 30px; height: 30px; flex: none; border-radius: 50%; background: var(--accent-soft); color: var(--accent); font-weight: 900; display: grid; place-items: center; font-size: 14px; }
.scene-num.done { background: var(--green-soft); color: var(--green); }
.scene-titles { flex: 1; min-width: 0; }
.scene-titles .t-fi { font-weight: 800; font-size: 16px; }
.scene-titles .t-zh { color: var(--muted); font-size: 13px; }
.scene-chevron { color: var(--muted); transition: transform .2s; font-size: 18px; }
.scene.open .scene-chevron { transform: rotate(90deg); }
.scene-body { display: none; padding: 0 18px 18px; border-top: 1px solid var(--line); }
.scene.open .scene-body { display: block; }

/* audio player */
.player { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; padding: 14px 0; }
.player audio { flex: 1; min-width: 200px; height: 38px; }
.speeds { display: inline-flex; gap: 4px; }
.speeds button { border: 1px solid var(--line); background: var(--panel); border-radius: 999px; padding: 4px 10px; font: inherit; font-size: 12px; font-weight: 700; color: var(--muted); cursor: pointer; }
.speeds button.on { background: var(--accent); color: #fff; border-color: var(--accent); }

/* lines */
.lines { display: flex; flex-direction: column; gap: 2px; }
.line { padding: 10px 12px; border-radius: 12px; }
.line:hover { background: var(--bg); }
.line .speaker { font-size: 12px; font-weight: 800; color: var(--accent); text-transform: uppercase; letter-spacing: .04em; }
.line .fi { font-size: 17px; font-weight: 600; }
.line .tr { font-size: 14px; color: var(--muted); margin-top: 2px; }
.line .tr.ja { font-family: "Noto Sans JP", sans-serif; }
.line .tr[hidden] { display: none; }

/* vocab */
.vocab { margin-top: 16px; }
.vocab h4 { margin: 0 0 8px; font-size: 13px; letter-spacing: .1em; text-transform: uppercase; color: var(--muted); }
.vocab-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 8px; }
.vocab-item { display: block; width: 100%; text-align: left; font: inherit; background: var(--bg); border: 1px solid var(--line); border-radius: 12px; padding: 10px 12px; cursor: pointer; transition: .12s; }
.vocab-item:hover:not(:disabled), .vocab-item.speaking { border-color: var(--accent); background: var(--accent-soft); }
.vocab-item:disabled { cursor: default; }
.vocab-item .v-fi { display: flex; align-items: center; gap: 7px; font-weight: 800; color: var(--accent-ink); }
.vocab-item .v-spk { font-size: 12px; opacity: .45; transition: .12s; }
.vocab-item:hover .v-spk, .vocab-item.speaking .v-spk { opacity: 1; }
.vocab-item.speaking .v-spk { animation: spk-pulse .7s ease-in-out infinite; }
@keyframes spk-pulse { 50% { transform: scale(1.25); } }
.vocab-item .v-tr { font-size: 13px; color: var(--muted); margin-top: 3px; }

/* ---------- practice ---------- */
.practice-pick { display: grid; grid-template-columns: repeat(auto-fill, minmax(200px,1fr)); gap: 12px; margin-top: 10px; }
.pp-card { background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius); box-shadow: var(--shadow); padding: 18px; cursor: pointer; transition: .15s; }
.pp-card:hover { border-color: var(--accent); transform: translateY(-2px); }
.pp-emoji { font-size: 28px; }
.pp-title { font-weight: 800; font-size: 16px; margin-top: 6px; }
.pp-desc { color: var(--muted); font-size: 13px; }

.quiz { background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius); box-shadow: var(--shadow); padding: 22px; margin-top: 12px; }
.quiz-top { display: flex; align-items: center; justify-content: space-between; margin-bottom: 6px; }
.quiz-top .qcount { color: var(--muted); font-weight: 700; font-size: 14px; }
.quiz-top .qexit { color: var(--muted); font-weight: 700; font-size: 14px; cursor: pointer; }
.quiz-prompt { font-size: 15px; color: var(--muted); margin-bottom: 4px; }
.quiz-q { font-family: var(--serif); font-size: 26px; font-weight: 600; margin: 6px 0 18px; letter-spacing: -.01em; }
.quiz-q.small { font-size: 20px; }
.quiz-q .fi { color: var(--accent-ink); }
.opts { display: grid; gap: 10px; }
.opt {
  text-align: left; border: 1.5px solid var(--line); background: var(--panel);
  border-radius: 12px; padding: 13px 16px; font: inherit; font-size: 16px; font-weight: 600;
  cursor: pointer; transition: .12s;
}
.opt:hover:not(:disabled) { border-color: var(--accent); background: var(--accent-soft); }
.opt.correct { border-color: var(--green); background: var(--green-soft); color: var(--green); }
.opt.wrong { border-color: var(--red); background: var(--red-soft); color: var(--red); }
.opt:disabled { cursor: default; }

.quiz-next { margin-top: 16px; display: flex; justify-content: flex-end; }
.btn { border: 0; background: var(--accent); color: #fff; font: inherit; font-weight: 800; font-size: 15px; padding: 10px 22px; border-radius: 999px; cursor: pointer; }
.btn:hover { filter: brightness(1.05); }
.btn.ghost { background: var(--panel); color: var(--accent); border: 1.5px solid var(--line); }

/* word ordering */
.build-target { min-height: 54px; border: 2px dashed var(--line); border-radius: 12px; padding: 10px; display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 14px; align-content: flex-start; }
.build-bank { display: flex; flex-wrap: wrap; gap: 8px; }
.chip { border: 1.5px solid var(--line); background: var(--bg); border-radius: 10px; padding: 8px 14px; font: inherit; font-size: 16px; font-weight: 700; cursor: pointer; }
.chip:hover { border-color: var(--accent); }
.chip.placed { background: var(--accent-soft); border-color: var(--accent); color: var(--accent); }
.build-hint { color: var(--muted); font-size: 14px; margin-bottom: 12px; }
.build-result { font-weight: 800; margin-top: 12px; }
.build-result.ok { color: var(--green); }
.build-result.no { color: var(--red); }

/* result screen */
.result { text-align: center; padding: 20px 0; }
.result .score { font-family: var(--serif); font-size: 54px; font-weight: 600; color: var(--accent); }
.result .emoji { font-size: 48px; }
.result .msg { color: var(--muted); margin: 6px 0 18px; }
.result .btns { display: flex; gap: 10px; justify-content: center; }

@media (max-width: 560px) {
  .topbar { flex-wrap: wrap; }
  .lang-pref { width: 100%; justify-content: space-between; }
}