:root {
  color-scheme: dark;
  --bg: #0f1115;
  --panel: #171a20;
  --panel-light: #1f2430;
  --text: #e6edf3;
  --muted: #9aa7b2;
  --accent: #6dd3ff;
  --accent-strong: #44bfff;
  --success: #45d483;
  --danger: #ff6b6b;
  --warning: #ffcc66;
  --border: #2b313a;
  --shadow: rgba(0, 0, 0, 0.4);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Segoe UI", system-ui, -apple-system, sans-serif;
  background: var(--bg);
  color: var(--text);
}

.app-shell {
  display: grid;
  grid-template-columns: 360px 1fr;
  min-height: 100vh;
}

.panel {
  background: var(--panel);
  padding: 24px;
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.panel-header h1 {
  margin: 0 0 8px;
  font-size: 22px;
}

.panel-header p {
  margin: 0;
  color: var(--muted);
  font-size: 14px;
}

.panel-section {
  background: var(--panel-light);
  padding: 16px;
  border-radius: 12px;
  box-shadow: 0 8px 20px var(--shadow);
}

.panel-section h2 {
  margin: 0 0 12px;
  font-size: 14px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--muted);
}

.field-grid {
  display: grid;
  gap: 12px;
}

label {
  display: flex;
  flex-direction: column;
  font-size: 13px;
  color: var(--muted);
  gap: 6px;
}

select,
input[type="number"] {
  background: #0f1218;
  border: 1px solid var(--border);
  color: var(--text);
  border-radius: 8px;
  padding: 8px 10px;
  font-size: 14px;
}

button {
  border: none;
  padding: 10px 14px;
  border-radius: 10px;
  font-weight: 600;
  cursor: pointer;
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}

button:hover {
  transform: translateY(-1px);
  box-shadow: 0 8px 20px rgba(0,0,0,0.35);
}

button.primary {
  background: var(--accent);
  color: #001018;
}

button.ghost {
  background: transparent;
  color: var(--text);
  border: 1px solid var(--border);
}

.panel-section button {
  width: 100%;
  margin-bottom: 10px;
}

.panel-section button:last-child {
  margin-bottom: 0;
}

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

.chip {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: #0f1218;
  border: 1px solid var(--border);
  padding: 6px 10px;
  border-radius: 999px;
  font-size: 13px;
  color: var(--muted);
}

.chip.disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

.chip.disabled input {
  cursor: not-allowed;
}

.chip input {
  accent-color: var(--accent);
}

.toggle {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 14px;
  color: var(--text);
}

.hint {
  margin-top: 8px;
  font-size: 12px;
  color: var(--muted);
}

.hint.is-problem {
  color: #ff8b8b;
  font-weight: 650;
}

.panel-footer {
  margin-top: auto;
  color: var(--muted);
  font-size: 12px;
}

.board {
  display: flex;
  flex-direction: column;
  gap: 20px;
  padding: 24px;
}

.game-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  align-items: center;
  background: var(--panel-light);
  padding: 12px 16px;
  border-radius: 14px;
  box-shadow: 0 10px 24px var(--shadow);
  position: sticky;
  top: 16px;
  z-index: 3;
}

.game-nav button {
  min-width: 140px;
}

.hud {
  display: flex;
  gap: 16px;
}

.stat {
  background: var(--panel-light);
  padding: 12px 18px;
  border-radius: 12px;
  box-shadow: 0 8px 20px var(--shadow);
  min-width: 140px;
}

.stat .label {
  display: block;
  font-size: 12px;
  color: var(--muted);
}

.stat .value {
  font-size: 20px;
  font-weight: 700;
}

.prompt {
  background: linear-gradient(135deg, rgba(68,191,255,0.2), rgba(31,36,48,0.9));
  padding: 18px 22px;
  border-radius: 16px;
  border: 1px solid rgba(109, 211, 255, 0.3);
  box-shadow: 0 12px 30px var(--shadow);
}

.prompt-title {
  text-transform: uppercase;
  letter-spacing: 0.12em;
  font-size: 12px;
  color: var(--muted);
}

.prompt-text {
  margin-top: 6px;
  font-size: 20px;
  font-weight: 700;
}

.prompt-detail {
  margin-top: 6px;
  font-size: 14px;
  color: var(--muted);
}

.prompt-feedback {
  margin-top: 8px;
  font-size: 14px;
  font-weight: 600;
}

.prompt-feedback.success {
  color: var(--success);
}

.prompt-feedback.fail {
  color: var(--danger);
}

.fretboard-frame {
  background: var(--panel-light);
  padding: 16px;
  border-radius: 16px;
  box-shadow: 0 12px 30px var(--shadow);
  overflow-x: auto;
}

#fretboard {
  min-height: 240px;
}

@media (max-width: 1024px) {
  .app-shell {
    grid-template-columns: 1fr;
  }
  .panel {
    border-right: none;
    border-bottom: 1px solid var(--border);
  }
}