/* ========== CSS 变量：深色主题（默认） ========== */
:root {
  --bg-primary: #0f172a;
  --bg-secondary: #1e293b;
  --bg-card: rgba(30, 41, 59, 0.8);
  --text-primary: #f1f5f9;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  --border-color: rgba(148, 163, 184, 0.3);
  --accent: #fbbf24;
  --accent-text: #111827;
  --success: #34d399;
  --success-text: #022c22;
  --nav-bg: rgba(15, 23, 42, 0.95);
}

/* ========== 浅色主题 ========== */
body.light-theme {
  --bg-primary: #f8fafc;
  --bg-secondary: #e2e8f0;
  --bg-card: rgba(255, 255, 255, 0.9);
  --text-primary: #1e293b;
  --text-secondary: #475569;
  --text-muted: #64748b;
  --border-color: rgba(100, 116, 139, 0.3);
  --accent: #f59e0b;
  --accent-text: #fff;
  --success: #10b981;
  --success-text: #fff;
  --nav-bg: rgba(241, 245, 249, 0.95);
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  transition: background 200ms ease, color 200ms ease;
}

/* ========== 导航栏 ========== */
.app-nav {
  display: flex;
  gap: 6px;
  padding: 10px 16px;
  border-bottom: 1px solid var(--border-color);
  background: var(--nav-bg);
  backdrop-filter: blur(10px);
  position: sticky;
  top: 0;
  z-index: 100;
}

.nav-btn {
  flex: 1;
  padding: 10px 12px;
  border-radius: 8px;
  border: 1px solid var(--border-color);
  background: transparent;
  color: var(--text-primary);
  cursor: pointer;
  font-size: 0.9rem;
  font-weight: 500;
  transition: all 150ms ease;
}

.nav-btn:hover {
  background: var(--bg-secondary);
}

.nav-btn.active {
  background: var(--accent);
  color: var(--accent-text);
  border-color: var(--accent);
}

/* 主题切换按钮 */
.theme-toggle {
  padding: 8px 12px;
  border-radius: 8px;
  border: 1px solid var(--border-color);
  background: var(--bg-secondary);
  color: var(--text-primary);
  cursor: pointer;
  font-size: 1rem;
  transition: all 150ms ease;
}

.theme-toggle:hover {
  background: var(--accent);
  color: var(--accent-text);
}

/* ========== 主内容区 ========== */
.app-main {
  flex: 1;
  padding: 20px 16px 32px;
  max-width: 800px;
  width: 100%;
  margin: 0 auto;
}

.page {
  display: none;
}

.page.active {
  display: block;
  animation: fadeIn 200ms ease;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

h2 {
  font-size: 1.1rem;
  margin-bottom: 16px;
  color: var(--text-primary);
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border-color);
}

h3 {
  font-size: 0.95rem;
  margin: 20px 0 12px;
  color: var(--text-secondary);
}

p {
  margin-bottom: 8px;
  line-height: 1.5;
  color: var(--text-secondary);
}

/* ========== 控制行布局 ========== */
.control-row {
  margin: 14px 0;
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  align-items: center;
  padding: 12px 14px;
  background: var(--bg-card);
  border-radius: 10px;
  border: 1px solid var(--border-color);
}

.control-row-center {
  justify-content: center;
}

/* ========== 和弦卡片 ========== */
.chord-list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 12px;
  margin-top: 12px;
}

.chord-card {
  padding: 12px;
  border-radius: 10px;
  border: 1px solid var(--border-color);
  background: var(--bg-card);
  transition: all 150ms ease;
}

.chord-card:hover {
  border-color: var(--accent);
}

.chord-header {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  margin-bottom: 8px;
}

.chord-name {
  font-weight: 600;
  font-size: 1.1rem;
  color: var(--accent);
}

.chord-diagram-wrapper {
  flex-shrink: 0;
}

.chord-diagram {
  display: block;
}

.chord-notes {
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-bottom: 4px;
}

.chord-usage {
  font-size: 0.8rem;
  color: var(--text-muted);
}

.chord-shape {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-top: 2px;
}

/* ========== 音阶卡片 ========== */
.scale-list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 12px;
  margin-top: 12px;
}

.scale-card {
  padding: 12px;
  border-radius: 10px;
  border: 1px solid var(--border-color);
  background: var(--bg-card);
  transition: all 150ms ease;
}

.scale-card:hover {
  border-color: var(--accent);
}

.scale-name {
  font-weight: 600;
  margin-bottom: 8px;
  color: var(--accent);
}

.scale-diagram-wrapper {
  margin-bottom: 8px;
}

.scale-diagram {
  display: block;
}

.scale-notes {
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-bottom: 4px;
}

.scale-usage,
.scale-tip {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-bottom: 2px;
}

.scale-actions {
  margin-top: 8px;
}

/* ========== 伴奏相关 ========== */
.backing-current-label {
  font-size: 0.9rem;
  color: var(--text-secondary);
  padding: 6px 12px;
  background: var(--bg-secondary);
  border-radius: 6px;
}

#backingCurrentChord {
  font-weight: 700;
  color: var(--accent);
  margin-left: 6px;
  font-size: 1rem;
}

.progression-container {
  margin-top: 16px;
  padding: 14px;
  background: var(--bg-card);
  border-radius: 10px;
  border: 1px solid var(--border-color);
}

.progression-title {
  font-size: 0.9rem;
  font-weight: 600;
  margin-bottom: 10px;
  color: var(--text-secondary);
}

.progression-row {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.progression-bar {
  min-width: 48px;
  padding: 8px 10px;
  border-radius: 8px;
  border: 1px solid var(--border-color);
  background: var(--bg-secondary);
  font-size: 0.85rem;
  font-weight: 500;
  text-align: center;
  transition: all 150ms ease;
}

.progression-bar.active {
  background: var(--accent);
  border-color: var(--accent);
  color: var(--accent-text);
  transform: scale(1.05);
}

.progression-note {
  margin-top: 10px;
  font-size: 0.8rem;
  color: var(--text-muted);
}

/* ========== 表单元素 ========== */
label {
  font-size: 0.9rem;
  display: flex;
  align-items: center;
  gap: 8px;
  color: var(--text-secondary);
}

select {
  font-size: 0.9rem;
  padding: 6px 10px;
  border-radius: 6px;
  border: 1px solid var(--border-color);
  background: var(--bg-secondary);
  color: var(--text-primary);
  cursor: pointer;
}

input[type="range"] {
  width: 180px;
  height: 8px;
  border-radius: 4px;
  background: linear-gradient(to right, var(--accent) 0%, var(--accent) 50%, var(--bg-secondary) 50%, var(--bg-secondary) 100%);
  cursor: pointer;
  -webkit-appearance: none;
}

/* 深色主题下进度条更深 */
:root {
  --range-track: #334155;
}

body.light-theme {
  --range-track: #cbd5e1;
}

input[type="range"]::-webkit-slider-runnable-track {
  height: 8px;
  border-radius: 4px;
  background: var(--range-track);
}

input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: var(--accent);
  cursor: pointer;
  margin-top: -5px;
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.3);
}

/* ========== 按钮 ========== */
button {
  padding: 10px 20px;
  border-radius: 8px;
  border: 1px solid var(--border-color);
  background: var(--bg-secondary);
  color: var(--text-primary);
  cursor: pointer;
  font-size: 0.9rem;
  font-weight: 500;
  transition: all 150ms ease;
}

button:hover:not(:disabled) {
  background: var(--accent);
  color: var(--accent-text);
  border-color: var(--accent);
}

button.primary {
  background: var(--success);
  border-color: var(--success);
  color: var(--success-text);
}

button.primary:hover:not(:disabled) {
  filter: brightness(1.1);
}

button:disabled {
  opacity: 0.5;
  cursor: default;
}

/* ========== 节拍器视觉 ========== */
.metronome-visual {
  width: 100px;
  height: 100px;
  border-radius: 50%;
  border: 3px solid var(--border-color);
  margin: 20px auto;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--bg-card);
  transition: all 100ms ease;
}

.metronome-visual.active {
  background: var(--accent);
  border-color: var(--accent);
  transform: scale(1.08);
}

#bpmValue {
  font-weight: 700;
  min-width: 40px;
  display: inline-block;
  text-align: center;
  margin: 0 6px;
  color: var(--accent);
  font-size: 1.1rem;
}

.bpm-step {
  padding: 4px 8px;
  border: 1px solid var(--border-color);
  border-radius: 4px;
  background: var(--bg-secondary);
  color: var(--text-primary);
  font-size: 0.9rem;
  cursor: pointer;
  transition: all 150ms ease;
}

.bpm-step:hover {
  background: var(--accent);
  color: var(--accent-text);
  border-color: var(--accent);
}

/* ========== 响应式 ========== */
@media (max-width: 600px) {
  .app-nav {
    padding: 8px 12px;
  }

  .nav-btn {
    padding: 8px 6px;
    font-size: 0.8rem;
  }

  .app-main {
    padding: 16px 12px 24px;
  }

  .control-row {
    padding: 10px 12px;
    gap: 12px;
  }

  input[type="range"] {
    width: 100%;
  }

  .chord-list,
  .scale-list {
    grid-template-columns: 1fr;
  }
}