:root {
  --bg: #fafaf9;
  --fg: #1c1917;
  --muted: #78716c;
  --border: #e7e5e4;
  --accent: #0369a1;
  --accent-soft: #e0f2fe;
  --chip-bg: #f5f5f4;
  --chip-active-bg: #0369a1;
  --chip-active-fg: #ffffff;
  --card-bg: #ffffff;
  --card-hover: #f8fafc;
}
* { box-sizing: border-box; }
html, body {
  margin: 0; padding: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu, "Helvetica Neue", sans-serif;
  background: var(--bg); color: var(--fg);
  font-size: 15px; line-height: 1.5;
}
header {
  padding: 1.5rem 2rem 1rem; border-bottom: 1px solid var(--border);
  background: var(--card-bg);
}
.title-row { display: flex; align-items: baseline; gap: 0.75rem; }
h1 { margin: 0; font-size: 1.5rem; font-weight: 700; }
.subtitle { color: var(--muted); font-size: 0.9rem; }
.admin-link {
  margin-left: auto; color: var(--muted); text-decoration: none; font-size: 0.85rem;
  padding: 0.25rem 0.6rem; border: 1px solid var(--border); border-radius: 6px;
}
.admin-link:hover { background: var(--chip-bg); color: var(--fg); }
.meta-row { color: var(--muted); font-size: 0.85rem; margin-top: 0.4rem; }

.controls {
  padding: 1rem 2rem; background: var(--card-bg);
  border-bottom: 1px solid var(--border);
  display: flex; flex-direction: column; gap: 0.6rem;
}
#search {
  width: 100%; padding: 0.65rem 0.9rem; font-size: 1rem;
  border: 1px solid var(--border); border-radius: 8px;
  background: var(--bg);
}
#search:focus { outline: 2px solid var(--accent); outline-offset: -1px; border-color: var(--accent); }

.filter-row { display: flex; align-items: center; gap: 0.5rem; flex-wrap: wrap; }
.filter-label { font-size: 0.8rem; color: var(--muted); width: 60px; text-transform: uppercase; letter-spacing: 0.05em; }
.chips { display: flex; flex-wrap: wrap; gap: 0.35rem; }
.chip {
  cursor: pointer; padding: 0.25rem 0.65rem; border-radius: 999px;
  background: var(--chip-bg); color: var(--fg); font-size: 0.82rem;
  border: 1px solid transparent; user-select: none;
}
.chip.active { background: var(--chip-active-bg); color: var(--chip-active-fg); }
.chip .count { opacity: 0.7; font-size: 0.75rem; margin-left: 0.3rem; }

select, button {
  font-family: inherit; font-size: 0.9rem;
  padding: 0.35rem 0.7rem; border: 1px solid var(--border); border-radius: 6px;
  background: var(--card-bg); color: var(--fg); cursor: pointer;
}
button.ghost { background: transparent; color: var(--muted); }
button.ghost:hover { background: var(--chip-bg); color: var(--fg); }

.selection-bar {
  position: sticky; top: 0; z-index: 50;
  display: flex; align-items: center; gap: 1rem; flex-wrap: wrap;
  padding: 0.6rem 2rem;
  background: var(--accent); color: white;
  box-shadow: 0 2px 8px rgba(0,0,0,0.08);
}
.selection-bar.hidden { display: none; }
.selection-bar label { display: inline-flex; align-items: center; gap: 0.4rem; font-size: 0.85rem; }
.selection-bar select { background: white; color: var(--fg); }
.selection-bar button { background: white; color: var(--accent); font-weight: 600; border-color: white; }
.selection-bar button.ghost { background: transparent; color: white; border-color: rgba(255,255,255,0.4); font-weight: 400; }
.selection-bar button.ghost:hover { background: rgba(255,255,255,0.15); }

main { padding: 1rem 2rem 4rem; }
.count-row { color: var(--muted); font-size: 0.85rem; margin-bottom: 0.75rem; }

.ref-card {
  display: flex; align-items: flex-start; gap: 0.75rem;
  padding: 0.7rem 0.9rem; margin-bottom: 0.4rem;
  background: var(--card-bg); border: 1px solid var(--border); border-radius: 8px;
}
.ref-card:hover { background: var(--card-hover); }
.ref-card.selected { border-color: var(--accent); background: var(--accent-soft); }
.ref-card input[type="checkbox"] { margin-top: 0.3rem; cursor: pointer; transform: scale(1.1); }
.ref-card .body { flex: 1; min-width: 0; }
.ref-card .citation { margin: 0; }
.ref-card .citation .authors { font-weight: 600; }
.ref-card .citation .year { color: var(--muted); }
.ref-card .citation .title { display: block; margin-top: 0.15rem; }
.ref-card .citation .container { font-style: italic; color: var(--muted); }
.ref-card .meta { display: flex; gap: 0.4rem; flex-wrap: wrap; margin-top: 0.35rem; font-size: 0.78rem; color: var(--muted); }
.ref-card .meta .tag {
  background: var(--chip-bg); padding: 0.1rem 0.5rem; border-radius: 999px; color: var(--fg);
}
.ref-card .meta .tag.chap { background: var(--accent-soft); color: var(--accent); }
.ref-card .meta .tag.added { background: #fef3c7; color: #92400e; }

/* ───── Chapter colour coding (cards + chips + meta tags) ───── */
/* Each chapter gets a soft background + saturated border / chip colour. */
.ref-card.chap-ch1 { border-left: 4px solid #0ea5e9; }
.ref-card.chap-ch2 { border-left: 4px solid #14b8a6; }
.ref-card.chap-ch3 { border-left: 4px solid #6366f1; }
.ref-card.chap-ch4 { border-left: 4px solid #f59e0b; }
.ref-card.chap-ch5 { border-left: 4px solid #dc2626; }
.ref-card.chap-ch6 { border-left: 4px solid #16a34a; }
.ref-card.chap-ch7 { border-left: 4px solid #8b5cf6; }
.ref-card.chap-ch8 { border-left: 4px solid #db2777; }
.ref-card.chap-ch9 { border-left: 4px solid #525252; }
.ref-card.chap-multi { border-left: 4px solid #1c1917; }

.tag.chap.ch-ch1 { background: #e0f2fe; color: #0369a1; }
.tag.chap.ch-ch2 { background: #ccfbf1; color: #0f766e; }
.tag.chap.ch-ch3 { background: #e0e7ff; color: #4338ca; }
.tag.chap.ch-ch4 { background: #fef3c7; color: #b45309; }
.tag.chap.ch-ch5 { background: #fee2e2; color: #b91c1c; }
.tag.chap.ch-ch6 { background: #dcfce7; color: #15803d; }
.tag.chap.ch-ch7 { background: #ede9fe; color: #6d28d9; }
.tag.chap.ch-ch8 { background: #fce7f3; color: #be185d; }
.tag.chap.ch-ch9 { background: #f5f5f4; color: #44403c; }

.chip[data-chap="ch1"].active { background: #0ea5e9; color: white; }
.chip[data-chap="ch2"].active { background: #14b8a6; color: white; }
.chip[data-chap="ch3"].active { background: #6366f1; color: white; }
.chip[data-chap="ch4"].active { background: #f59e0b; color: white; }
.chip[data-chap="ch5"].active { background: #dc2626; color: white; }
.chip[data-chap="ch6"].active { background: #16a34a; color: white; }
.chip[data-chap="ch7"].active { background: #8b5cf6; color: white; }
.chip[data-chap="ch8"].active { background: #db2777; color: white; }
.chip[data-chap="ch9"].active { background: #525252; color: white; }

/* Date-added filter input */
.date-filter input[type="date"],
.date-filter select {
  font-family: inherit; font-size: 0.85rem;
  padding: 0.3rem 0.5rem; border: 1px solid var(--border); border-radius: 6px;
  background: var(--bg); color: var(--fg);
}
.date-filter .date-preset.active {
  background: var(--accent); color: white; border-color: var(--accent);
}
.ref-card .notes {
  margin-top: 0.4rem; padding: 0.4rem 0.6rem;
  background: #fefce8; border-left: 3px solid #facc15;
  font-size: 0.84rem; color: #422006; white-space: pre-wrap;
  border-radius: 0 6px 6px 0;
}
.ref-card .meta a { color: var(--accent); text-decoration: none; }
.ref-card .meta a:hover { text-decoration: underline; }
.ref-card .actions { display: flex; flex-direction: column; gap: 0.25rem; }
.ref-card .actions button {
  font-size: 0.72rem; padding: 0.2rem 0.5rem; color: var(--muted);
  background: transparent; border: 1px solid var(--border);
}
.ref-card .actions button:hover { color: var(--accent); border-color: var(--accent); }
.ref-card .actions .btn {
  font-size: 0.72rem; padding: 0.2rem 0.5rem; color: var(--muted);
  background: transparent; border: 1px solid var(--border); border-radius: 6px;
  text-decoration: none; text-align: center; display: inline-block;
}
.ref-card .actions .btn:hover { color: var(--accent); border-color: var(--accent); }
.ref-card .actions .pdf-btn { color: #b91c1c; border-color: #fecaca; }
.ref-card .actions .pdf-btn:hover { color: #991b1b; border-color: #f87171; background: #fef2f2; }
.ref-card .actions .edit-link { opacity: 0.5; }
.ref-card .actions .edit-link:hover { opacity: 1; }
.ref-card .sim-score {
  font-size: 0.72rem; font-weight: 600; color: var(--accent);
  background: var(--accent-soft); padding: 0.15rem 0.45rem;
  border-radius: 999px; text-align: center; min-width: 2.5rem;
}
.sim-banner {
  background: var(--accent-soft); color: var(--accent);
  padding: 0.5rem 0.8rem; border-radius: 8px; margin-bottom: 0.5rem;
  font-size: 0.9rem;
}
.sim-banner a { color: var(--accent); text-decoration: underline; }

footer {
  text-align: center; padding: 1rem; color: var(--muted); font-size: 0.8rem;
  border-top: 1px solid var(--border);
}

.empty {
  padding: 3rem 1rem; text-align: center; color: var(--muted);
}

@media (max-width: 640px) {
  header, .controls, .selection-bar, main { padding-left: 1rem; padding-right: 1rem; }
  .filter-label { width: auto; }
  .title-row { flex-wrap: wrap; }
}