:root {
  --bg: #ffffff;
  --fg: #1a1a1a;
  --muted: #6b6b6b;
  --border: #e3e3e3;
  --accent: #2563eb;
  --accent-fg: #ffffff;
  --star: #eab308;
  --card-bg: #f7f7f8;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #121212;
    --fg: #f0f0f0;
    --muted: #9a9a9a;
    --border: #2b2b2b;
    --accent: #5b9bff;
    --accent-fg: #0a0a0a;
    --star: #facc15;
    --card-bg: #1c1c1e;
  }
}

* { box-sizing: border-box; }

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

.hidden { display: none !important; }

/* PIN screen */
.pin-screen {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1rem;
}
.pin-screen form {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  width: 100%;
  max-width: 280px;
}
.pin-screen h1 { text-align: center; margin: 0 0 0.5rem; }
.pin-screen input {
  font-size: 1.25rem;
  padding: 0.75rem;
  text-align: center;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--card-bg);
  color: var(--fg);
}
.pin-screen button {
  font-size: 1rem;
  padding: 0.75rem;
  border: none;
  border-radius: 8px;
  background: var(--accent);
  color: var(--accent-fg);
  cursor: pointer;
}
.error { color: #dc2626; text-align: center; min-height: 1.2em; margin: 0; }

/* App shell */
.app {
  max-width: 720px;
  margin: 0 auto;
  padding: 0 0.75rem 2rem;
}
.topbar {
  position: sticky;
  top: 0;
  background: var(--bg);
  padding-top: 0.75rem;
  padding-bottom: 0.5rem;
  z-index: 10;
  border-bottom: 1px solid var(--border);
}
.topbar h1 { margin: 0; font-size: 1.25rem; }

.topbar-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
}

.sync-btn {
  padding: 0.4rem 0.7rem;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--card-bg);
  color: var(--fg);
  font-size: 0.8rem;
  cursor: pointer;
}
.sync-btn:disabled { opacity: 0.5; cursor: default; }

.sync-status {
  font-size: 0.72rem;
  color: var(--muted);
  margin: 0.3rem 0 0.5rem;
  min-height: 1em;
}
.sync-status.error { color: #dc2626; }

.tabs { display: flex; gap: 0.5rem; }
.tab-btn {
  flex: 1;
  padding: 0.6rem;
  border: 1px solid var(--border);
  background: var(--card-bg);
  color: var(--fg);
  border-radius: 8px;
  cursor: pointer;
  font-size: 0.9rem;
}
.tab-btn.active { background: var(--accent); color: var(--accent-fg); border-color: var(--accent); }

.tab-panel { display: none; padding-top: 0.75rem; }
.tab-panel.active { display: block; }

.controls {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 0.75rem;
  flex-wrap: wrap;
}
.controls select, .controls button, .controls input {
  padding: 0.5rem;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--card-bg);
  color: var(--fg);
  font-size: 0.85rem;
  min-width: 0;
}
.controls select {
  max-width: 60%;
  text-overflow: ellipsis;
  white-space: nowrap;
  overflow: hidden;
}
.search-box {
  flex: 1 1 100%;
  font-size: 0.95rem;
  max-width: 100%;
}
.mode-btn.active { background: var(--accent); color: var(--accent-fg); border-color: var(--accent); }
#review-shuffle-btn { margin-left: auto; cursor: pointer; }

.book-group { margin-bottom: 1.25rem; }
.book-group h2 {
  font-size: 1rem;
  margin: 0 0 0.5rem;
  color: var(--muted);
}

.card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 0.75rem;
  margin-bottom: 0.6rem;
}
.card-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 0.5rem;
}
.card-book { font-size: 0.75rem; color: var(--muted); margin-bottom: 0.25rem; }
.card-text { white-space: pre-wrap; line-height: 1.4; }
.card-meta { font-size: 0.75rem; color: var(--muted); margin-top: 0.35rem; }

.star-btn {
  border: none;
  background: none;
  font-size: 1.25rem;
  cursor: pointer;
  line-height: 1;
  color: var(--border);
  flex-shrink: 0;
}
.star-btn.starred { color: var(--star); }

.comment-box {
  width: 100%;
  margin-top: 0.5rem;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--bg);
  color: var(--fg);
  padding: 0.5rem;
  font-family: inherit;
  font-size: 0.9rem;
  resize: vertical;
  min-height: 2.2em;
}
.comment-saved { font-size: 0.7rem; color: var(--muted); }

.empty-state { color: var(--muted); text-align: center; padding: 2rem 1rem; }