:root { --accent: #0a7cff; --bg: #fff; --fg: #111; --muted: #666; --border: #ddd; }
* { box-sizing: border-box; }
html, body { margin: 0; font-family: -apple-system, system-ui, sans-serif; color: var(--fg); background: var(--bg); }
body { padding: env(safe-area-inset-top) 16px env(safe-area-inset-bottom); }
h1, h2 { margin: 16px 0; }
button { font: inherit; padding: 12px 16px; border-radius: 8px; border: 1px solid var(--border); background: #f6f6f6; cursor: pointer; }
button.primary { background: var(--accent); color: white; border-color: var(--accent); }
button:disabled { opacity: 0.5; }
.screen { max-width: 640px; margin: 0 auto; }
.book { padding: 12px; border: 1px solid var(--border); border-radius: 8px; margin-bottom: 8px; display: flex; justify-content: space-between; align-items: center; }
.choice { display: block; width: 100%; margin: 8px 0; text-align: left; }
.choice.correct { background: #c7f3d2; border-color: #6cc17f; }
.choice.wrong   { background: #f7c7c7; border-color: #d86a6a; }
.muted { color: var(--muted); font-size: 14px; }
.progress { height: 4px; background: #eee; border-radius: 2px; overflow: hidden; margin: 8px 0 16px; }
.progress > div { height: 100%; background: var(--accent); transition: width 0.2s; }
.error { color: #c00; }