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

:root {
  --color-primary: #b8860b;
  --color-primary-light: #d4a540;
  --color-primary-dark: #8b6508;
  --color-bg: #faf6f0;
  --color-surface: #f0e9de;
  --color-surface-hover: #e6ddd0;
  --color-text: #2c1810;
  --color-muted: #8b7355;
  --color-correct: #4a7c59;
  --color-correct-bg: #e6efe8;
  --color-wrong: #8b4513;
  --color-wrong-bg: #f5ece8;
  --color-missed-bg: #f5f0e0;
  --font-sans: -apple-system, BlinkMacSystemFont, "SF Pro Display", "SF Pro Text", system-ui, sans-serif;
  --radius: 10px;
}

html.dark {
  --color-primary: #d4a540;
  --color-primary-light: #e6be5a;
  --color-primary-dark: #c49530;
  --color-bg: #1a1612;
  --color-surface: #2a2420;
  --color-surface-hover: #3a322c;
  --color-text: #e8e0d4;
  --color-muted: #a89880;
  --color-correct: #7db88a;
  --color-correct-bg: #1e2e22;
  --color-wrong: #c97a5a;
  --color-wrong-bg: #2e1e18;
  --color-missed-bg: #2e2810;
}

body {
  font-family: var(--font-sans);
  background: var(--color-bg);
  color: var(--color-text);
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
  transition: background 0.3s, color 0.3s;
}

#app {
  flex: 1;
  display: flex;
  flex-direction: column;
  max-width: 640px;
  margin: 0 auto;
  width: 100%;
  padding: 1rem 1rem 0;
}

/* ---- Header ---- */

.app-header {
  padding: 1.25rem 0 0.75rem;
  text-align: center;
  position: relative;
}

.app-header h1 {
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--color-primary-dark);
  letter-spacing: 0.02em;
}

.app-header .subtitle {
  font-size: 0.8rem;
  color: var(--color-muted);
  margin-top: 0.2rem;
  letter-spacing: 0.15em;
  text-transform: uppercase;
}

/* ---- Tabs ---- */

.tabs {
  display: flex;
  gap: 0;
  border-bottom: 1px solid var(--color-surface);
  margin-bottom: 1rem;
}

.tab {
  flex: 1;
  padding: 0.6rem 0;
  border: none;
  background: none;
  font-family: inherit;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--color-muted);
  cursor: pointer;
  border-bottom: 2px solid transparent;
  margin-bottom: -1px;
  transition: color 0.2s, border-color 0.2s;
}

.tab:hover {
  color: var(--color-primary);
}

.tab.active {
  color: var(--color-primary-dark);
  border-bottom-color: var(--color-primary);
}

/* ---- Sub-tabs ---- */

.sub-tabs {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 1rem;
  justify-content: center;
}

.sub-tab {
  padding: 0.3rem 1.2rem;
  border: 1px solid var(--color-surface);
  border-radius: 999px;
  background: var(--color-surface);
  font-family: inherit;
  font-size: 0.825rem;
  color: var(--color-muted);
  cursor: pointer;
  transition: all 0.2s;
}

.sub-tab:hover {
  background: var(--color-surface-hover);
}

.sub-tab.active {
  background: var(--color-primary);
  border-color: var(--color-primary);
  color: #fff;
}

/* ---- Main ---- */

.app-main {
  flex: 1;
}

.section {
  display: none;
}

.section.active {
  display: block;
}

/* ---- Question ---- */

.question-prompt {
  font-size: 1.35rem;
  font-weight: 600;
  text-align: center;
  padding: 1.5rem 0 1.25rem;
  color: var(--color-text);
}

/* ---- Button group ---- */

.btn-group {
  display: grid;
  gap: 0.5rem;
}

.btn {
  font-family: inherit;
  font-size: 0.9rem;
  border: none;
  border-radius: var(--radius);
  cursor: pointer;
  transition: background 0.15s, transform 0.1s, box-shadow 0.15s;
}

.btn:active:not(:disabled) {
  transform: scale(0.96);
}

.btn-option {
  padding: 0.55rem 1rem;
  min-width: 3.5rem;
  background: var(--color-surface);
  color: var(--color-text);
  border: 1px solid transparent;
}

.btn-option:hover:not(:disabled) {
  background: var(--color-surface-hover);
  border-color: var(--color-primary-light);
}

.btn-option.selected {
  background: var(--color-primary);
  color: #fff;
  border-color: var(--color-primary-dark);
}

.btn-option.correct {
  background: var(--color-correct-bg);
  color: var(--color-correct);
  border-color: var(--color-correct);
  font-weight: 600;
}

.btn-option.wrong {
  background: var(--color-wrong-bg);
  color: var(--color-wrong);
  border-color: var(--color-wrong);
  font-weight: 600;
}

.btn-option.missed {
  background: var(--color-missed-bg);
  color: var(--color-primary-dark);
  border-color: var(--color-primary);
  font-weight: 600;
}

.btn-option:disabled {
  cursor: default;
  opacity: 0.85;
}

.btn-submit {
  display: block;
  margin: 1rem auto 0;
  padding: 0.55rem 2.5rem;
  background: var(--color-primary);
  color: #fff;
  font-weight: 600;
  border-radius: 999px;
}

.btn-submit:hover:not(:disabled) {
  background: var(--color-primary-light);
}

.btn-submit:disabled {
  opacity: 0.5;
  cursor: default;
}

/* ---- Feedback ---- */

.feedback {
  text-align: center;
  margin-top: 1rem;
  padding: 0.6rem 1rem;
  border-radius: var(--radius);
  font-weight: 500;
  font-size: 0.95rem;
}

.feedback-correct {
  background: var(--color-correct-bg);
  color: var(--color-correct);
}

.feedback-wrong {
  background: var(--color-wrong-bg);
  color: var(--color-wrong);
}

.btn-next {
  display: block;
  margin: 1rem auto 0;
  padding: 0.55rem 2.5rem;
  background: var(--color-primary);
  color: #fff;
  font-weight: 600;
  border-radius: 999px;
}

.btn-next:hover {
  background: var(--color-primary-light);
}

/* ---- Score bar ---- */

.score-bar {
  display: flex;
  align-items: center;
  position: relative;
  padding: 0.75rem 0;
  color: var(--color-muted);
  font-size: 0.85rem;
  border-top: 1px solid var(--color-surface);
  margin-top: auto;
  letter-spacing: 0.05em;
}

.score-bar #score {
  flex: 1;
  text-align: center;
}

/* ---- Theme toggle ---- */

.github-link {
  position: absolute;
  left: 0;
  font-size: 0.75rem;
  color: var(--color-muted);
  text-decoration: none;
  padding: 0.25rem 0;
  transition: color 0.2s;
}

.github-link:hover {
  color: var(--color-primary);
}

.theme-toggle {
  position: absolute;
  right: 0;
  border: none;
  background: none;
  cursor: pointer;
  font-family: inherit;
  font-size: 0.75rem;
  color: var(--color-muted);
  padding: 0.25rem 0;
  transition: color 0.2s;
}

.theme-toggle:hover {
  color: var(--color-primary);
}

/* ---- Jazz decoration ---- */

.jazz-notes {
  text-align: center;
  padding: 0.25rem 0 0;
  font-size: 1.1rem;
  letter-spacing: 0.4em;
  color: var(--color-primary-light);
  opacity: 0.5;
  user-select: none;
}