:root {
  --bg-primary: #0a0d14;
  --bg-secondary: #121722;
  --bg-tertiary: #19202f;
  --bg-card: rgba(18, 23, 34, 0.85);
  --bg-hover: rgba(255, 255, 255, 0.06);

  --border-color: rgba(255, 255, 255, 0.1);
  --border-focus: #6366f1;

  --text-main: #f1f5f9;
  --text-muted: #94a3b8;
  --text-dim: #64748b;

  --accent-primary: #6366f1;
  --accent-primary-hover: #4f46e5;
  --accent-secondary: #06b6d4;
  --accent-success: #10b981;
  --accent-success-hover: #059669;
  --accent-chord: #f59e0b;
  --accent-chord-bg: rgba(245, 158, 11, 0.15);
  --accent-section: #38bdf8;

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-full: 9999px;

  --font-sans: 'Plus Jakarta Sans', -apple-system, BlinkMacSystemFont, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', monospace;

  --shadow-glow: 0 0 25px rgba(99, 102, 241, 0.25);
  --shadow-card: 0 10px 30px -10px rgba(0, 0, 0, 0.5);
  --backdrop-blur: blur(12px);
}

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

body {
  background-color: var(--bg-primary);
  background-image: 
    radial-gradient(circle at 15% 10%, rgba(99, 102, 241, 0.15) 0%, transparent 40%),
    radial-gradient(circle at 85% 80%, rgba(6, 182, 212, 0.12) 0%, transparent 40%),
    radial-gradient(circle at 50% 50%, rgba(16, 185, 129, 0.05) 0%, transparent 50%);
  color: var(--text-main);
  font-family: var(--font-sans);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

/* App Container */
.app-container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 1.5rem 2rem;
  width: 100%;
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
  flex: 1;
}

/* Header */
.app-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--border-color);
}

.logo-group {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.logo-icon {
  width: 48px;
  height: 48px;
  border-radius: var(--radius-md);
  background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  box-shadow: var(--shadow-glow);
}

.logo-title {
  font-size: 1.6rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  background: linear-gradient(to right, #ffffff, #cbd5e1);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.logo-title span {
  background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.logo-subtitle {
  font-size: 0.85rem;
  color: var(--text-muted);
}

/* Toolbar Card */
.toolbar-card {
  background: var(--bg-card);
  backdrop-filter: var(--backdrop-blur);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 1.25rem 1.5rem;
  box-shadow: var(--shadow-card);
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.options-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 1rem;
}

.toggle-control {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  cursor: pointer;
  padding: 0.5rem 0.75rem;
  border-radius: var(--radius-md);
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid rgba(255, 255, 255, 0.05);
  transition: all 0.2s ease;
}

.toggle-control:hover {
  background: var(--bg-hover);
  border-color: rgba(255, 255, 255, 0.12);
}

.toggle-control input[type="checkbox"] {
  display: none;
}

.toggle-slider {
  width: 40px;
  height: 22px;
  background: var(--bg-tertiary);
  border-radius: var(--radius-full);
  position: relative;
  transition: background 0.25s ease;
  flex-shrink: 0;
  border: 1px solid var(--border-color);
}

.toggle-slider::after {
  content: '';
  position: absolute;
  top: 2px;
  left: 2px;
  width: 16px;
  height: 16px;
  background: white;
  border-radius: 50%;
  transition: transform 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

.toggle-control input:checked + .toggle-slider {
  background: var(--accent-primary);
  border-color: var(--accent-primary);
}

.toggle-control input:checked + .toggle-slider::after {
  transform: translateX(18px);
}

.toggle-label {
  display: flex;
  flex-direction: column;
  gap: 0.15rem;
}

.toggle-label strong {
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--text-main);
}

.toggle-label small {
  font-size: 0.75rem;
  color: var(--text-muted);
}

/* Sub Toolbar */
.sub-toolbar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding-top: 1rem;
  border-top: 1px solid rgba(255, 255, 255, 0.06);
}

.control-group {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  font-size: 0.85rem;
  color: var(--text-muted);
}

.select-input {
  background: var(--bg-secondary);
  color: var(--text-main);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  padding: 0.4rem 0.75rem;
  font-size: 0.85rem;
  font-family: inherit;
  outline: none;
  cursor: pointer;
  transition: border-color 0.2s;
}

.select-input:focus {
  border-color: var(--accent-primary);
}

.transpose-value {
  display: inline-block;
  min-width: 28px;
  text-align: center;
  font-family: var(--font-mono);
  font-weight: 700;
  color: var(--accent-secondary);
}

/* Editor Grid */
.editor-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.25rem;
  min-height: 480px;
}

@media (max-width: 900px) {
  .editor-grid {
    grid-template-columns: 1fr;
  }
}

.card {
  background: var(--bg-card);
  backdrop-filter: var(--backdrop-blur);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  display: flex;
  flex-direction: column;
  box-shadow: var(--shadow-card);
  overflow: hidden;
}

.card-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.85rem 1.25rem;
  background: rgba(255, 255, 255, 0.02);
  border-bottom: 1px solid var(--border-color);
}

.header-left {
  display: flex;
  align-items: center;
  gap: 0.6rem;
}

.card-header h2 {
  font-size: 0.95rem;
  font-weight: 600;
}

.view-toggle {
  display: flex;
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  padding: 2px;
}

.view-btn {
  background: none;
  border: none;
  color: var(--text-muted);
  font-size: 0.75rem;
  padding: 0.25rem 0.6rem;
  border-radius: 4px;
  cursor: pointer;
  font-family: inherit;
  transition: all 0.2s;
}

.view-btn.active {
  background: var(--accent-primary);
  color: white;
  font-weight: 600;
}

.card-body {
  position: relative;
  flex: 1;
  display: flex;
  flex-direction: column;
  min-height: 380px;
}

textarea {
  width: 100%;
  height: 100%;
  flex: 1;
  background: transparent;
  border: none;
  padding: 1.25rem;
  color: var(--text-main);
  font-family: var(--font-mono);
  font-size: 0.9rem;
  line-height: 1.7;
  resize: vertical;
  outline: none;
  white-space: pre;
}

textarea::placeholder {
  color: var(--text-dim);
}

.output-preview {
  position: absolute;
  inset: 0;
  padding: 1.25rem;
  overflow-y: auto;
  font-family: var(--font-mono);
  font-size: 0.9rem;
  line-height: 1.8;
  white-space: pre-wrap;
  background: var(--bg-card);
}

.output-preview.hidden {
  display: none;
}

.output-preview .chord-badge {
  color: var(--accent-chord);
  font-weight: 700;
  background: var(--accent-chord-bg);
  padding: 1px 4px;
  border-radius: 4px;
  margin-right: 1px;
}

.output-preview .section-header {
  color: var(--accent-section);
  font-weight: 700;
  display: block;
  margin-top: 1rem;
  margin-bottom: 0.25rem;
}

.output-preview .meta-line {
  color: var(--accent-secondary);
  font-weight: 600;
  display: block;
}

.output-preview .meta-divider {
  color: var(--text-dim);
  display: block;
  margin-bottom: 0.5rem;
}

.card-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.75rem 1.25rem;
  border-top: 1px solid var(--border-color);
  background: rgba(255, 255, 255, 0.01);
  font-size: 0.8rem;
}

/* Rules / Badges Card */
.rules-card {
  background: rgba(18, 23, 34, 0.6);
  border: 1px dashed var(--border-color);
  border-radius: var(--radius-md);
  padding: 1rem 1.5rem;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.rules-header {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  color: var(--accent-secondary);
}

.rules-header h3 {
  font-size: 0.9rem;
  font-weight: 600;
}

.rules-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
}

.rule-tag {
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid rgba(255, 255, 255, 0.08);
  padding: 0.35rem 0.75rem;
  border-radius: var(--radius-sm);
  font-size: 0.8rem;
  color: var(--text-muted);
}

.rule-tag strong {
  color: var(--text-main);
}

/* Buttons & Badges */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  padding: 0.5rem 1rem;
  font-size: 0.85rem;
  font-weight: 600;
  font-family: inherit;
  border-radius: var(--radius-sm);
  border: 1px solid transparent;
  cursor: pointer;
  transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  text-decoration: none;
  white-space: nowrap;
}

.btn-primary {
  background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
  color: white;
  box-shadow: 0 4px 14px rgba(99, 102, 241, 0.35);
}

.btn-primary:hover {
  transform: translateY(-1px);
  box-shadow: 0 6px 18px rgba(99, 102, 241, 0.45);
}

.btn-success {
  background: var(--accent-success);
  color: white;
}

.btn-success:hover {
  background: var(--accent-success-hover);
}

.btn-secondary {
  background: var(--bg-tertiary);
  color: var(--text-main);
  border-color: var(--border-color);
}

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

.btn-outline {
  background: transparent;
  color: var(--text-main);
  border-color: var(--border-color);
}

.btn-outline:hover {
  background: var(--bg-hover);
  border-color: rgba(255, 255, 255, 0.2);
}

.btn-sm {
  padding: 0.35rem 0.75rem;
  font-size: 0.8rem;
}

.btn-xs {
  padding: 0.25rem 0.55rem;
  font-size: 0.75rem;
}

.btn-icon {
  width: 28px;
  height: 28px;
  padding: 0;
  border-radius: 4px;
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  color: var(--text-main);
}

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

.btn-group {
  display: flex;
  align-items: center;
  gap: 0.35rem;
}

.badge {
  font-size: 0.72rem;
  font-weight: 700;
  padding: 0.2rem 0.5rem;
  border-radius: var(--radius-sm);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.badge-primary {
  background: rgba(99, 102, 241, 0.15);
  color: #818cf8;
  border: 1px solid rgba(99, 102, 241, 0.3);
}

.badge-success {
  background: rgba(16, 185, 129, 0.15);
  color: #34d399;
  border: 1px solid rgba(16, 185, 129, 0.3);
}

.badge-pill {
  background: rgba(255, 255, 255, 0.05);
  color: var(--text-muted);
  font-size: 0.75rem;
}

/* Toast */
.toast {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  background: var(--bg-secondary);
  color: var(--text-main);
  padding: 0.75rem 1.25rem;
  border-radius: var(--radius-md);
  border: 1px solid var(--accent-success);
  box-shadow: 0 10px 25px rgba(0, 0, 0, 0.5);
  display: flex;
  align-items: center;
  gap: 0.5rem;
  transform: translateY(100px);
  opacity: 0;
  pointer-events: none;
  transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  z-index: 1000;
}

.toast.show {
  transform: translateY(0);
  opacity: 1;
}

/* Footer */
.app-footer {
  text-align: center;
  padding: 1.5rem 0 0.5rem;
  font-size: 0.8rem;
  color: var(--text-dim);
}