:root {
  --bg: #1a1410;
  --bg2: #241c15;
  --panel: #2b2117;
  --panel2: #34281c;
  --line: #443422;
  --wood: #c98a3c;
  --wood-d: #a9712d;
  --ink: #f3e7d6;
  --ink-dim: #b9a991;
  --ok: #6fcf73;
  --no: #e9695f;
  --accent: #e0a049;
  --radius: 14px;
  --shadow: 0 6px 24px rgba(0,0,0,.35);
}
* { box-sizing: border-box; }
html, body { margin: 0; }
body {
  font-family: "Segoe UI", system-ui, -apple-system, "PingFang SC", "Microsoft YaHei", sans-serif;
  background: radial-gradient(1200px 600px at 50% -10%, #2a2016, var(--bg)) fixed;
  color: var(--ink);
  min-height: 100vh;
  -webkit-tap-highlight-color: transparent;
}

/* ---- top bar ---- */
.topbar {
  display: flex; align-items: center; justify-content: space-between;
  padding: 12px 16px; padding-top: max(12px, env(safe-area-inset-top));
  background: linear-gradient(180deg, rgba(0,0,0,.25), transparent);
}
.brand { font-size: 19px; font-weight: 700; letter-spacing: .5px; }
.brand span { background: linear-gradient(90deg, var(--wood), var(--accent)); -webkit-background-clip: text; background-clip: text; color: transparent; }
.sound-btn {
  background: var(--panel); color: var(--ink); border: 1px solid var(--line);
  border-radius: 999px; padding: 7px 14px; font-size: 14px; cursor: pointer;
}
.sound-btn.off { color: var(--ink-dim); }
.sound-btn:disabled { opacity: .4; }

/* ---- tabs ---- */
.tabs {
  display: flex; gap: 6px; padding: 0 12px 4px; max-width: 760px; margin: 0 auto;
}
.tab {
  flex: 1; background: transparent; color: var(--ink-dim);
  border: none; border-bottom: 2px solid transparent;
  padding: 12px 6px; font-size: 15px; font-weight: 600; cursor: pointer;
  transition: color .15s, border-color .15s;
}
.tab.on { color: var(--ink); border-bottom-color: var(--accent); }

/* ---- view ---- */
.view { max-width: 760px; margin: 0 auto; padding: 14px 14px 40px; }
.practice { display: flex; flex-direction: column; gap: 16px; }

.practice-bar {
  display: flex; flex-wrap: wrap; gap: 12px; align-items: center; justify-content: space-between;
}
.seg { display: inline-flex; background: var(--bg2); border: 1px solid var(--line); border-radius: 999px; padding: 3px; }
.seg button {
  background: transparent; color: var(--ink-dim); border: none; cursor: pointer;
  padding: 7px 13px; font-size: 13.5px; border-radius: 999px; font-weight: 600;
}
.seg button.on { background: var(--wood); color: #20160c; }
.switch { display: inline-flex; align-items: center; gap: 7px; color: var(--ink-dim); font-size: 14px; cursor: pointer; }
.switch input { accent-color: var(--accent); width: 16px; height: 16px; }

.prompt { font-size: 18px; line-height: 1.5; text-align: center; padding: 4px 2px; }
.prompt .hint { color: var(--ink-dim); font-size: 14px; }
.prompt .big { color: var(--accent); font-size: 1.35em; }

/* ---- board / diagram cards ---- */
.board, .diagram {
  background: linear-gradient(180deg, var(--panel2), var(--panel));
  border: 1px solid var(--line); border-radius: var(--radius); box-shadow: var(--shadow);
  padding: 14px; display: flex; justify-content: center; align-items: center; min-height: 90px;
}
.board { overflow-x: auto; }
.fretboard-svg { width: 100%; min-width: 540px; height: auto; }
.chord-svg { width: 168px; height: auto; }
.hidden-card, .hint-card {
  color: var(--ink-dim); font-size: 15px; text-align: center;
}
.hidden-card { font-size: 40px; color: var(--wood-d); }

/* ---- answers ---- */
.answers { display: flex; flex-wrap: wrap; gap: 10px; justify-content: center; }
.choice {
  background: var(--panel); color: var(--ink); border: 1px solid var(--line);
  border-radius: 12px; padding: 12px 16px; min-width: 52px; font-size: 17px; font-weight: 600;
  cursor: pointer; transition: transform .08s, background .15s, border-color .15s;
}
.choice:hover { border-color: var(--wood-d); }
.choice:active { transform: scale(.96); }
.choice:disabled { cursor: default; }
.choice.correct { background: rgba(111,207,115,.18); border-color: var(--ok); color: var(--ok); }
.choice.wrong { background: rgba(233,105,95,.16); border-color: var(--no); color: var(--no); }
.choice.g-good { border-color: var(--ok); }
.choice.g-bad { border-color: var(--no); }
.fretgrid { display: grid; grid-template-columns: repeat(6, 1fr); gap: 8px; width: 100%; max-width: 420px; }
.fretbtn { min-width: 0; padding: 12px 0; }
.selfgrade { display: flex; gap: 10px; justify-content: center; }
.selfgrade-q { width: 100%; text-align: center; color: var(--ink-dim); margin-bottom: 8px; }

/* ---- feedback ---- */
.feedback { text-align: center; font-size: 16px; min-height: 26px; display: flex; flex-direction: column; align-items: center; gap: 12px; }
.feedback.ok { color: var(--ok); }
.feedback.no { color: var(--no); }
.next-btn {
  background: linear-gradient(180deg, var(--wood), var(--wood-d)); color: #20160c;
  border: none; border-radius: 12px; padding: 12px 22px; font-size: 16px; font-weight: 700; cursor: pointer;
}
.next-btn:active { transform: scale(.97); }
.scoreline { text-align: center; color: var(--ink-dim); font-size: 14px; }
.foot { text-align: center; color: #6f5d45; font-size: 12px; padding: 20px; }

/* ---- SVG: fretboard ---- */
.fb-fretnum { fill: #7d6a4f; font-size: 11px; }
.fb-inlay { fill: #6a563b; }
.fb-nut { fill: #efe2cb; }
.fb-wire { stroke: #5a4731; stroke-width: 2; }
.fb-string { stroke: #d8c39a; }
.fb-openlabel { fill: var(--ink-dim); font-size: 12px; font-weight: 600; }
.fb-hit { fill: transparent; cursor: pointer; }
.fb-hit:hover { fill: rgba(224,160,73,.18); }
.fb-dot circle { fill: var(--wood); }
.fb-dot .fb-dotlabel { fill: #20160c; font-size: 12px; font-weight: 700; }
.fb-dot.ask circle { fill: var(--accent); }
.fb-dot.good circle { fill: var(--ok); }
.fb-dot.bad circle { fill: var(--no); }
.fb-dot.hintdot circle { fill: rgba(224,160,73,.35); }
.fb-dot.hintdot .fb-dotlabel { fill: var(--ink); }
.fb-dot.nat circle { fill: var(--wood); }
.fb-dot.nat .fb-dotlabel { fill: #20160c; }
.fb-dot.acc circle { fill: #4f3d28; }
.fb-dot.acc .fb-dotlabel { fill: var(--ink-dim); font-size: 10px; }

/* ---- reference view ---- */
.ref-seg { display: flex; margin: 0 auto 4px; }
.ref-seg button { flex: 1; }
.ref-note { color: var(--ink-dim); font-size: 13.5px; text-align: center; line-height: 1.7; }
.swatch { display: inline-block; width: 12px; height: 12px; border-radius: 3px; vertical-align: -1px; margin: 0 4px 0 10px; }
.swatch.nat { background: var(--wood); }
.swatch.acc { background: #4f3d28; }
.card-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(140px, 1fr)); gap: 12px; }
.ref-card {
  background: linear-gradient(180deg, var(--panel2), var(--panel));
  border: 1px solid var(--line); border-radius: var(--radius); box-shadow: var(--shadow);
  padding: 10px; display: flex; justify-content: center; cursor: pointer;
  transition: border-color .15s, transform .08s;
}
.ref-card:hover { border-color: var(--wood-d); }
.ref-card:active { transform: scale(.98); }
.barre-block { margin-bottom: 22px; }
.barre-h { font-size: 16px; margin: 14px 2px 10px; }
.barre-sub { color: var(--ink-dim); font-size: 13px; font-weight: 400; }
.barre-cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(120px, 1fr)); gap: 12px; margin-bottom: 12px; }
.barre-cards .ref-card { cursor: pointer; }
.barre-table { min-width: 200px; }
.bt-head { color: var(--ink-dim); font-size: 13px; margin-bottom: 8px; }
.bt-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(64px, 1fr)); gap: 6px; }
.bt-cell {
  background: var(--bg2); border: 1px solid var(--line); border-radius: 8px;
  padding: 6px 4px; text-align: center; font-size: 13px; color: var(--ink);
}
.bt-cell b { color: var(--accent); margin-right: 3px; }

/* ---- SVG: chord diagram ---- */
.chord-title { fill: var(--ink); font-size: 16px; font-weight: 700; }
.chord-basefret { fill: var(--ink-dim); font-size: 11px; }
.chord-nut { fill: #efe2cb; }
.chord-string { stroke: #cdb78d; stroke-width: 1.4; }
.chord-fret { stroke: #5a4731; stroke-width: 1.4; }
.chord-dot { fill: var(--wood); }
.chord-finger { fill: #20160c; font-size: 11px; font-weight: 700; }
.chord-open { fill: none; stroke: var(--ink-dim); stroke-width: 1.5; }
.chord-x { fill: var(--ink-dim); font-size: 13px; font-weight: 700; }
.chord-barre { fill: var(--wood-d); opacity: .92; }
.chord-strnote { fill: var(--ink-dim); font-size: 11px; }

@media (max-width: 560px) {
  .prompt { font-size: 16px; }
  .seg button { padding: 7px 10px; font-size: 12.5px; }
  .view { padding: 12px 10px 40px; }
}