/* =========================================================
   烏克麗麗 3D 互動教學手冊 — 樣式
   以 CSS 自訂屬性管理色彩與間距；支援深淺主題與 RWD。
   ========================================================= */

:root {
  color-scheme: light;
  --font-sans: "Noto Sans TC", "PingFang TC", "Microsoft JhengHei", "Heiti TC",
    system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;

  --bg: #faf6ef;
  --bg-elev: #ffffff;
  --bg-muted: #f1eadf;
  --fg: #2a211a;
  --fg-muted: #6b5d51;
  --border: #e2d7c7;
  --accent: #b45309;
  --accent-strong: #92400e;
  --accent-soft: #fde8c8;
  --accent-fg: #ffffff;
  --info: #1d4ed8;
  --info-soft: #dbeafe;
  --success: #15803d;
  --success-soft: #dcfce7;
  --danger: #b91c1c;
  --shadow: 0 1px 2px rgb(42 33 26 / 0.06), 0 8px 24px rgb(42 33 26 / 0.08);
  --stage-bg: radial-gradient(circle at 50% 35%, #fffaf2 0%, #efe4d2 70%, #e6d8c2 100%);

  --radius: 12px;
  --radius-sm: 8px;
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.5rem;
  --space-6: 2rem;
  --header-h: 3.5rem;
  --focus: 0 0 0 3px var(--bg), 0 0 0 6px var(--info);
}

:root[data-theme="dark"] {
  color-scheme: dark;
  --bg: #17130f;
  --bg-elev: #221c16;
  --bg-muted: #2b241d;
  --fg: #f3ebe0;
  --fg-muted: #b8a897;
  --border: #3b3128;
  --accent: #f59e0b;
  --accent-strong: #fbbf24;
  --accent-soft: #3d2a10;
  --accent-fg: #1a1208;
  --info: #93c5fd;
  --info-soft: #1e2a44;
  --success: #86efac;
  --success-soft: #14321f;
  --danger: #fca5a5;
  --shadow: 0 1px 2px rgb(0 0 0 / 0.4), 0 8px 24px rgb(0 0 0 / 0.45);
  --stage-bg: radial-gradient(circle at 50% 35%, #2e261e 0%, #1a1511 70%, #120e0b 100%);
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  height: 100%;
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100%;
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.65;
  color: var(--fg);
  background: var(--bg);
  display: flex;
  flex-direction: column;
}

img,
svg,
canvas {
  max-width: 100%;
  display: block;
}

button,
input,
select {
  font: inherit;
  color: inherit;
}

a {
  color: var(--info);
  text-underline-offset: 0.15em;
}

:focus-visible {
  outline: none;
  box-shadow: var(--focus);
  border-radius: var(--radius-sm);
}

.visually-hidden {
  position: absolute !important;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}

.skip-link {
  position: absolute;
  top: -100%;
  left: var(--space-4);
  z-index: 100;
  padding: var(--space-2) var(--space-4);
  background: var(--accent);
  color: var(--accent-fg);
  border-radius: 0 0 var(--radius-sm) var(--radius-sm);
  text-decoration: none;
}
.skip-link:focus {
  top: 0;
}

/* ---------- Header ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  align-items: center;
  gap: var(--space-4);
  min-height: var(--header-h);
  padding: 0 var(--space-4);
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}

.brand {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  margin: 0;
  font-size: 1.05rem;
  font-weight: 700;
  white-space: nowrap;
  letter-spacing: 0.01em;
}
.brand svg {
  width: 1.75rem;
  height: 1.75rem;
  color: var(--accent);
}
.brand small {
  font-weight: 500;
  color: var(--fg-muted);
  font-size: 0.8rem;
}

.step-nav {
  flex: 1;
  min-width: 0;
  overflow-x: auto;
  scrollbar-width: thin;
}
.step-nav ol {
  display: flex;
  gap: var(--space-1);
  margin: 0;
  padding: var(--space-1) 0;
  list-style: none;
}
.step-nav button {
  display: inline-flex;
  align-items: center;
  gap: 0.4em;
  padding: 0.35rem 0.7rem;
  border: 1px solid transparent;
  border-radius: 999px;
  background: transparent;
  color: var(--fg-muted);
  cursor: pointer;
  white-space: nowrap;
  font-size: 0.9rem;
}
.step-nav button .num {
  display: inline-grid;
  place-items: center;
  width: 1.4em;
  height: 1.4em;
  border-radius: 50%;
  background: var(--bg-muted);
  font-size: 0.75em;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
}
.step-nav button:hover {
  background: var(--bg-muted);
  color: var(--fg);
}
.step-nav button[aria-current="step"] {
  background: var(--accent-soft);
  color: var(--accent-strong);
  border-color: color-mix(in srgb, var(--accent) 35%, transparent);
  font-weight: 600;
}
.step-nav button[aria-current="step"] .num {
  background: var(--accent);
  color: var(--accent-fg);
}

.icon-button {
  display: inline-grid;
  place-items: center;
  width: 2.5rem;
  height: 2.5rem;
  padding: 0;
  border: 1px solid var(--border);
  border-radius: 50%;
  background: var(--bg-elev);
  cursor: pointer;
  flex-shrink: 0;
}
.icon-button:hover {
  background: var(--bg-muted);
}
.icon-button svg {
  width: 1.25rem;
  height: 1.25rem;
}
.theme-toggle .icon-sun {
  display: none;
}
:root[data-theme="dark"] .theme-toggle .icon-sun {
  display: block;
}
:root[data-theme="dark"] .theme-toggle .icon-moon {
  display: none;
}

/* ---------- Layout ---------- */
.layout {
  flex: 1;
  display: grid;
  grid-template-columns: minmax(0, 1.15fr) minmax(0, 1fr);
  gap: var(--space-4);
  padding: var(--space-4);
  max-width: 1400px;
  width: 100%;
  margin: 0 auto;
}

/* ---------- 3D Stage ---------- */
.stage {
  position: sticky;
  top: calc(var(--header-h) + var(--space-4));
  height: calc(100vh - var(--header-h) - var(--space-4) * 2);
  height: calc(100dvh - var(--header-h) - var(--space-4) * 2);
  min-height: 320px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--stage-bg);
  box-shadow: var(--shadow);
  overflow: hidden;
  display: grid;
  grid-template-rows: 1fr;
  isolation: isolate;
}
.stage canvas {
  width: 100%;
  height: 100%;
  touch-action: none;
  outline: none;
}
.stage canvas.is-pointer {
  cursor: pointer;
}
.stage .stage-inner {
  position: relative;
  grid-area: 1 / 1;
}
.stage-labels {
  position: absolute;
  inset: 0;
  pointer-events: none;
  overflow: hidden;
}
.stage-label {
  position: absolute;
  transform: translate(-50%, calc(-100% - 10px));
  pointer-events: auto;
  padding: 0.15rem 0.55rem;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: color-mix(in srgb, var(--bg-elev) 92%, transparent);
  color: var(--fg);
  font-size: 0.78rem;
  line-height: 1.5;
  white-space: nowrap;
  cursor: pointer;
  box-shadow: var(--shadow);
  transition: opacity 0.15s ease;
}
.stage-label::after {
  content: "";
  position: absolute;
  left: 50%;
  top: 100%;
  width: 1px;
  height: 10px;
  background: var(--fg-muted);
}
.stage-label[hidden] {
  display: none;
}
.stage-label.is-active {
  background: var(--accent);
  color: var(--accent-fg);
  border-color: var(--accent);
}

.stage-toolbar {
  position: absolute;
  left: var(--space-3);
  right: var(--space-3);
  bottom: var(--space-3);
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  align-items: center;
  justify-content: space-between;
  pointer-events: none;
}
.stage-toolbar > * {
  pointer-events: auto;
}
.view-group {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-1);
  padding: var(--space-1);
  border: 1px solid var(--border);
  border-radius: 999px;
  background: color-mix(in srgb, var(--bg-elev) 90%, transparent);
  backdrop-filter: blur(6px);
}
.view-group button,
.chip {
  padding: 0.3rem 0.75rem;
  border: 1px solid transparent;
  border-radius: 999px;
  background: transparent;
  cursor: pointer;
  font-size: 0.85rem;
  color: var(--fg);
}
.view-group button:hover {
  background: var(--bg-muted);
}
.view-group button[aria-pressed="true"] {
  background: var(--accent);
  color: var(--accent-fg);
}
.stage-hint {
  position: absolute;
  top: var(--space-3);
  left: var(--space-3);
  right: var(--space-3);
  display: flex;
  justify-content: space-between;
  gap: var(--space-2);
  font-size: 0.8rem;
  color: var(--fg-muted);
  pointer-events: none;
}
.stage-hint span {
  padding: 0.15rem 0.6rem;
  border-radius: 999px;
  background: color-mix(in srgb, var(--bg-elev) 80%, transparent);
}
.stage-status {
  position: absolute;
  top: var(--space-3);
  left: 50%;
  transform: translateX(-50%);
  padding: 0.25rem 0.9rem;
  border-radius: 999px;
  background: var(--fg);
  color: var(--bg);
  font-size: 0.85rem;
  opacity: 0;
  transition: opacity 0.2s ease;
  pointer-events: none;
}
.stage-status.is-visible {
  opacity: 0.92;
}
.stage-fallback {
  position: absolute;
  inset: 0;
  display: grid;
  place-content: center;
  gap: var(--space-2);
  padding: var(--space-5);
  text-align: center;
  color: var(--fg-muted);
}

/* ---------- Content Panel ---------- */
.panel {
  display: flex;
  flex-direction: column;
  min-width: 0;
}
.step-content {
  flex: 1;
  scroll-margin-top: calc(var(--header-h) + var(--space-3));
  padding: var(--space-5);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--bg-elev);
  box-shadow: var(--shadow);
}
.step-content h2 {
  margin: 0 0 var(--space-2);
  font-size: 1.6rem;
  line-height: 1.3;
}
.step-content h3 {
  margin: var(--space-5) 0 var(--space-2);
  font-size: 1.1rem;
}
.step-kicker {
  margin: 0;
  color: var(--accent);
  font-weight: 600;
  font-size: 0.85rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}
.step-intro {
  color: var(--fg-muted);
  margin-top: 0;
}
.step-content p,
.step-content li {
  overflow-wrap: anywhere;
}
.step-content ul,
.step-content ol {
  padding-left: 1.4em;
}
.step-content kbd {
  font-family: var(--font-mono);
  font-size: 0.85em;
  padding: 0.05em 0.4em;
  border: 1px solid var(--border);
  border-bottom-width: 2px;
  border-radius: 6px;
  background: var(--bg-muted);
}

.callout {
  display: flex;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-4);
  margin: var(--space-4) 0;
  border-radius: var(--radius-sm);
  border-left: 4px solid var(--info);
  background: var(--info-soft);
}
.callout.is-tip {
  border-left-color: var(--success);
  background: var(--success-soft);
}
.callout.is-warn {
  border-left-color: var(--accent);
  background: var(--accent-soft);
}
.callout p {
  margin: 0;
}
.callout strong {
  display: block;
  margin-bottom: 0.15em;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.45em;
  min-height: 2.5rem;
  padding: 0.45rem 1rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--bg-elev);
  color: var(--fg);
  cursor: pointer;
  text-decoration: none;
  line-height: 1.2;
}
.btn:hover {
  background: var(--bg-muted);
}
.btn.is-primary {
  background: var(--accent);
  border-color: var(--accent);
  color: var(--accent-fg);
  font-weight: 600;
}
.btn.is-primary:hover {
  background: var(--accent-strong);
  border-color: var(--accent-strong);
}
.btn[aria-pressed="true"] {
  background: var(--accent-soft);
  border-color: var(--accent);
  color: var(--accent-strong);
  font-weight: 600;
}
.btn.is-primary[aria-pressed="true"] {
  background: var(--accent-strong);
  border-color: var(--accent-strong);
  color: var(--accent-fg);
}
.btn:disabled {
  opacity: 0.55;
  cursor: not-allowed;
}
.btn svg {
  width: 1.1em;
  height: 1.1em;
}
.btn-row {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin: var(--space-3) 0;
}

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
  gap: var(--space-2);
  margin: var(--space-3) 0;
  padding: 0;
  list-style: none;
}
.card-grid button {
  width: 100%;
  min-height: 3rem;
  text-align: left;
  padding: 0.6rem 0.8rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--bg-elev);
  cursor: pointer;
  display: flex;
  flex-direction: column;
  gap: 0.1em;
}
.card-grid button:hover {
  border-color: var(--accent);
}
.card-grid button[aria-pressed="true"] {
  background: var(--accent-soft);
  border-color: var(--accent);
}
.card-grid button strong {
  font-size: 1rem;
}
.card-grid button small {
  color: var(--fg-muted);
  font-size: 0.78rem;
}

.detail-card {
  margin-top: var(--space-4);
  padding: var(--space-4);
  border-radius: var(--radius-sm);
  background: var(--bg-muted);
}
.detail-card h3 {
  margin-top: 0;
}
.detail-card .en {
  color: var(--fg-muted);
  font-weight: 400;
  font-size: 0.9rem;
  margin-left: 0.4em;
}

.field {
  display: grid;
  gap: var(--space-1);
  margin: var(--space-3) 0;
}
.field label {
  font-weight: 600;
  font-size: 0.9rem;
}
.field-inline {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-3);
}
input[type="range"] {
  width: min(100%, 260px);
  accent-color: var(--accent);
}
.toggle {
  display: inline-flex;
  align-items: center;
  gap: 0.5em;
  cursor: pointer;
  font-size: 0.9rem;
}
.toggle .label-short {
  display: none;
}
.toggle input {
  width: 1.1rem;
  height: 1.1rem;
  accent-color: var(--accent);
}

table.data {
  width: 100%;
  border-collapse: collapse;
  margin: var(--space-3) 0;
  font-variant-numeric: tabular-nums;
}
table.data th,
table.data td {
  padding: 0.5rem 0.6rem;
  border-bottom: 1px solid var(--border);
  text-align: left;
  vertical-align: middle;
}
table.data th {
  font-size: 0.85rem;
  color: var(--fg-muted);
}
.table-wrap {
  overflow-x: auto;
}

.panel-nav {
  display: flex;
  justify-content: space-between;
  gap: var(--space-2);
  margin-top: var(--space-4);
}
.panel-nav .btn {
  flex: 1;
}
.panel-nav .btn[disabled] {
  visibility: hidden;
}

/* 進度條 */
.progress {
  height: 4px;
  margin: 0 0 var(--space-3);
  border-radius: 999px;
  background: var(--bg-muted);
  overflow: hidden;
}
.progress > span {
  display: block;
  height: 100%;
  background: var(--accent);
  transition: width 0.3s ease;
}

/* ---------- Footer ---------- */
.site-footer {
  padding: var(--space-5) var(--space-4) var(--space-6);
  border-top: 1px solid var(--border);
  color: var(--fg-muted);
  font-size: 0.85rem;
  text-align: center;
}
.site-footer p {
  margin: 0.25em 0;
}
.site-footer a {
  color: var(--fg);
  font-weight: 600;
}

/* ---------- 動態 ---------- */
@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
  *,
  *::before,
  *::after {
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
  }
}

/* ---------- RWD ---------- */
@media (max-width: 960px) {
  .layout {
    grid-template-columns: 1fr;
    padding: var(--space-3);
    gap: var(--space-3);
  }
  .stage {
    top: calc(var(--header-h) + var(--space-3));
    height: 42vh;
    height: 42dvh;
    min-height: 260px;
    z-index: 10;
  }
  .stage-hint {
    display: none;
  }
  .step-content {
    padding: var(--space-4);
    scroll-margin-top: calc(var(--header-h) + 42dvh + var(--space-3) * 2);
  }
  .step-content h2 {
    font-size: 1.35rem;
  }
}

@media (max-width: 600px) {
  .brand span.text {
    display: none;
  }
  .site-header {
    gap: var(--space-2);
    padding: 0 var(--space-3);
  }
  .step-nav button .label {
    display: none;
  }
  .step-nav button[aria-current="step"] .label {
    display: inline;
  }
  .view-group button {
    padding: 0.3rem 0.55rem;
    font-size: 0.8rem;
  }
  .toggle .label-full {
    display: none;
  }
  .toggle .label-short {
    display: inline;
  }
}

/* ---------- 和弦 ---------- */
.chord-grid {
  grid-template-columns: repeat(auto-fill, minmax(110px, 1fr));
}
.chord-grid button strong {
  font-size: 1.25rem;
}
.chord-detail-grid {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: var(--space-4);
  align-items: start;
}
.chord-diagram {
  color: var(--fg);
  padding: var(--space-2);
  border-radius: var(--radius-sm);
  background: var(--bg-elev);
  border: 1px solid var(--border);
}
.chord-diagram svg {
  width: 150px;
  height: auto;
}
.fingering-list {
  margin: var(--space-2) 0;
  padding-left: 1.2em;
  font-size: 0.95rem;
}
@media (max-width: 600px) {
  .chord-detail-grid {
    grid-template-columns: 1fr;
    justify-items: center;
  }
  .chord-detail-grid > div:last-child {
    justify-self: stretch;
  }
}

/* ---------- 刷弦節奏 ---------- */
.strum-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(2.6rem, 1fr));
  gap: var(--space-1);
  margin-bottom: var(--space-3);
}
.strum-slot {
  display: grid;
  justify-items: center;
  gap: 0.1rem;
  padding: 0.4rem 0.2rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--bg-elev);
  transition: transform 0.08s ease, background 0.08s ease;
}
.strum-slot.is-beat {
  border-color: color-mix(in srgb, var(--fg) 30%, var(--border));
}
.strum-slot .strum-beat {
  font-size: 0.75rem;
  color: var(--fg-muted);
  font-variant-numeric: tabular-nums;
}
.strum-slot .strum-arrow {
  font-size: 1.5rem;
  line-height: 1.1;
  font-weight: 700;
}
.strum-slot .strum-text {
  font-size: 0.75rem;
}
.strum-slot.sym-D .strum-arrow {
  color: var(--accent);
}
.strum-slot.sym-U .strum-arrow {
  color: var(--info);
}
.strum-slot.sym-rest .strum-arrow {
  color: var(--fg-muted);
}
.strum-slot.sym-x .strum-arrow {
  color: var(--danger);
}
.strum-slot.is-active {
  background: var(--accent-soft);
  border-color: var(--accent);
  transform: translateY(-3px);
}
select {
  min-height: 2.5rem;
  padding: 0.35rem 0.6rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--bg-elev);
}

/* ---------- 練習曲 ---------- */
.song-meta {
  color: var(--fg-muted);
  font-size: 0.9rem;
}
.song-chords {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin: var(--space-3) 0;
}
.song-chord {
  margin: 0;
  text-align: center;
  cursor: pointer;
  border-radius: var(--radius-sm);
}
.song-chord .chord-diagram {
  padding: 0;
}
.song-chord .chord-diagram svg {
  width: 84px;
}
.song-chord figcaption {
  font-weight: 700;
  font-size: 0.95rem;
}
.song-chord.is-active .chord-diagram {
  border-color: var(--accent);
  background: var(--accent-soft);
}
.song-bars {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: var(--space-2);
  margin: var(--space-3) 0;
}
.song-bar {
  position: relative;
  display: grid;
  gap: 0.2rem;
  padding: 0.5rem 0.4rem 0.6rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--bg-elev);
  text-align: center;
  transition: background 0.1s ease, border-color 0.1s ease;
}
.song-bar-num {
  position: absolute;
  top: 0.2rem;
  left: 0.4rem;
  font-size: 0.7rem;
  color: var(--fg-muted);
}
.song-bar-chord {
  font-size: 1.35rem;
  font-weight: 700;
  padding-top: 0.4rem;
}
.song-bar-beats {
  display: flex;
  justify-content: center;
  gap: 0.25rem;
}
.song-bar-beats i {
  width: 0.5rem;
  height: 0.5rem;
  border-radius: 50%;
  background: var(--bg-muted);
  border: 1px solid var(--border);
}
.song-bar-beats i.is-on {
  background: var(--accent);
  border-color: var(--accent);
}
.song-bar.is-active {
  border-color: var(--accent);
  background: var(--accent-soft);
}
.song-tips {
  margin: var(--space-3) 0 0;
  padding-left: 1.2em;
  font-size: 0.95rem;
}
@media (max-width: 600px) {
  .song-bars {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}