/* ============================================================
   SPAR Project Page — HKUST theme
   Primary  : HKUST Blue   #003366
   Accent   : HKUST Gold   #9D7E4E / #B5985A
   ============================================================ */

:root {
  --hkust-blue: #003366;
  --hkust-blue-700: #002a52;
  --hkust-blue-500: #0a4a86;
  --hkust-blue-300: #2f6fae;
  --hkust-gold: #9d7e4e;
  --hkust-gold-light: #b5985a;
  --hkust-gold-soft: #e9dfca;

  --ink: #1c2530;
  --ink-soft: #4a5663;
  --muted: #7a8693;
  --line: #e3e8ee;
  --bg: #ffffff;
  --bg-alt: #f5f7fa;
  --bg-card: #ffffff;
  --shadow: 0 1px 2px rgba(0, 51, 102, 0.06), 0 8px 24px rgba(0, 51, 102, 0.08);
  --shadow-lg: 0 12px 40px rgba(0, 51, 102, 0.16);
  --radius: 14px;
  --radius-sm: 10px;
  --maxw: 1120px;

  --font: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
    "Helvetica Neue", Arial, "PingFang SC", "Microsoft YaHei", sans-serif;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; scroll-padding-top: 76px; }

body {
  margin: 0;
  font-family: var(--font);
  color: var(--ink);
  background: var(--bg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

a { color: var(--hkust-blue-500); text-decoration: none; }
a:hover { text-decoration: underline; }

img { max-width: 100%; display: block; }

.container { width: 100%; max-width: var(--maxw); margin: 0 auto; padding: 0 24px; }

.muted { color: var(--muted); }
.small { font-size: 0.85rem; }

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--hkust-blue);
  color: #fff;
  padding: 10px 16px;
  z-index: 1000;
  border-radius: 0 0 8px 0;
}
.skip-link:focus { left: 0; }

/* ---------- Topbar ---------- */
.topbar {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.86);
  backdrop-filter: saturate(160%) blur(12px);
  border-bottom: 1px solid var(--line);
}
.topbar__inner {
  display: flex;
  align-items: center;
  gap: 18px;
  height: 64px;
}
.brand { display: flex; align-items: center; gap: 10px; }
.brand__text {
  font-weight: 800;
  font-size: 1.35rem;
  letter-spacing: 0.06em;
  color: var(--hkust-blue);
}
.brand:hover { text-decoration: none; }

.nav { display: flex; gap: 6px; margin-left: 8px; }
.nav__link {
  color: var(--ink-soft);
  font-weight: 600;
  font-size: 0.92rem;
  padding: 8px 12px;
  border-radius: 8px;
  transition: background 0.15s, color 0.15s;
}
.nav__link:hover { background: var(--bg-alt); color: var(--hkust-blue); text-decoration: none; }

.partnerLogos { margin-left: auto; display: flex; align-items: center; gap: 14px; }
.partnerLogos__img { height: 40px; width: auto; max-width: 210px; }

/* ---------- Hero ---------- */
.hero {
  position: relative;
  padding: 56px 0 24px;
  background:
    radial-gradient(1100px 480px at 50% -120px, rgba(0, 51, 102, 0.10), transparent 60%),
    linear-gradient(180deg, #fbfcfe 0%, #ffffff 100%);
  border-bottom: 1px solid var(--line);
}
.hero__grid { text-align: center; }

.hero__title { margin: 6px 0 18px; line-height: 1.15; }
.hero__title--big {
  font-size: 4rem;
  font-weight: 900;
  letter-spacing: 0.04em;
  background: linear-gradient(120deg, var(--hkust-blue) 0%, var(--hkust-blue-500) 50%, var(--hkust-gold) 130%);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}
.hero__subtitle {
  display: inline-block;
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--ink);
  margin-top: 4px;
}

.hero__authors { font-size: 1.02rem; color: var(--ink); margin: 4px auto 4px; max-width: 880px; }
.hero__authors .author { color: var(--hkust-blue-500); font-weight: 600; }
.hero__authors sup { color: var(--hkust-gold); font-weight: 700; }
.hero__affil { color: var(--ink-soft); font-size: 0.95rem; margin: 6px 0 2px; }
.hero__affil sup { color: var(--hkust-gold); font-weight: 700; }
.hero__note { color: var(--muted); font-size: 0.85rem; margin: 0 0 20px; }

.cta-row { display: flex; flex-wrap: wrap; gap: 12px; justify-content: center; margin: 18px 0 8px; }

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-weight: 700;
  font-size: 0.95rem;
  padding: 11px 20px;
  border-radius: 999px;
  background: var(--hkust-blue);
  color: #fff;
  border: 1px solid var(--hkust-blue);
  transition: transform 0.12s, box-shadow 0.15s, background 0.15s;
  box-shadow: var(--shadow);
}
.btn:hover { background: var(--hkust-blue-700); text-decoration: none; transform: translateY(-1px); box-shadow: var(--shadow-lg); }
.btn--ghost { background: #fff; color: var(--hkust-blue); border-color: #cdd9e6; box-shadow: none; }
.btn--ghost:hover { background: var(--bg-alt); }
.btn--primary { background: var(--hkust-gold); border-color: var(--hkust-gold); }
.btn--primary:hover { background: var(--hkust-gold-light); }

/* ---------- Hook cards ---------- */
.hook { margin: 34px auto 6px; max-width: var(--maxw); text-align: left; }
.hook__headline {
  text-align: center;
  font-weight: 900;
  font-size: 1.4rem;
  color: var(--hkust-blue);
  margin-bottom: 18px;
}
.hook__grid { margin-top: 8px; }
.hook__card { border-top: 4px solid var(--hkust-blue); }
.hook__card--warn { border-top-color: #c0392b; }
.hook__card--bad { border-top-color: var(--hkust-gold); }
.hook__card--good { border-top-color: #1e7d4f; }
.hook__card--future { border-top-color: var(--hkust-blue-500); }
.hook__title { font-weight: 800; color: var(--ink); margin-bottom: 8px; font-size: 1.02rem; }
.hook__body { color: var(--ink-soft); font-size: 0.92rem; margin: 0; }

/* ---------- Hero key figure ---------- */
.hero__keyFigure { margin-top: 30px; }
.heroKeyFull { max-width: 980px; margin: 0 auto; }

/* ---------- Sections ---------- */
.section { padding: 64px 0; }
.section--alt { background: var(--bg-alt); }
.section h2 {
  font-size: 2rem;
  font-weight: 900;
  color: var(--hkust-blue);
  margin: 0 0 28px;
  text-align: center;
  position: relative;
}
.section h2::after {
  content: "";
  display: block;
  width: 64px;
  height: 4px;
  margin: 12px auto 0;
  border-radius: 2px;
  background: linear-gradient(90deg, var(--hkust-blue), var(--hkust-gold));
}

.prose { font-size: 1.02rem; color: var(--ink-soft); max-width: 920px; margin: 0 auto; }
.prose p { margin: 0 0 14px; }
.prose strong { color: var(--ink); }

/* ---------- Grid & cards ---------- */
.grid { display: grid; gap: 22px; margin-bottom: 22px; }
.grid--2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid--4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }
.span-2 { grid-column: 1 / -1; }

.card {
  background: var(--bg-card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 20px;
  box-shadow: var(--shadow);
}
.card__title { font-weight: 800; color: var(--hkust-blue); margin-bottom: 12px; font-size: 1.08rem; }
.card__body { color: var(--ink-soft); margin: 0 0 14px; }
.card--media { padding: 16px; }

.caption { color: var(--ink-soft); font-size: 0.9rem; margin-top: 12px; }
.caption b { color: var(--ink); }

.bullets { margin: 6px 0 0; padding-left: 20px; color: var(--ink-soft); }
.bullets li { margin-bottom: 8px; }
.bullets--tight li { margin-bottom: 10px; }
.bullets b { color: var(--ink); }

.analysis__body { color: var(--ink-soft); margin: 0 0 12px; }

/* ---------- Math ---------- */
.math-block {
  background: #f3f6fa;
  border: 1px solid #e0e8f1;
  border-radius: var(--radius-sm);
  padding: 14px 16px;
  margin: 14px 0;
  overflow-x: auto;
  text-align: center;
}

/* ---------- Media / images ---------- */
.media {
  position: relative;
  display: block;
  width: 100%;
  padding: 0;
  border: none;
  background: #fbfcfe;
  border-radius: var(--radius-sm);
  overflow: hidden;
  cursor: zoom-in;
}
.media img { width: 100%; height: auto; }
.media__hint {
  position: absolute;
  right: 10px;
  bottom: 10px;
  font-size: 0.74rem;
  font-weight: 600;
  color: #fff;
  background: rgba(0, 51, 102, 0.74);
  padding: 4px 9px;
  border-radius: 999px;
  opacity: 0;
  transition: opacity 0.15s;
}
.media:hover .media__hint { opacity: 1; }

/* ---------- Tables ---------- */
.table-wrap { overflow-x: auto; border-radius: var(--radius-sm); border: 1px solid var(--line); }
.table { width: 100%; border-collapse: collapse; font-size: 0.9rem; min-width: 540px; }
.table th, .table td { padding: 9px 12px; text-align: center; border-bottom: 1px solid var(--line); }
.table th:first-child, .table td:first-child { text-align: left; }
.table thead th {
  background: var(--hkust-blue);
  color: #fff;
  font-weight: 700;
  border-bottom: none;
  position: sticky;
  top: 0;
}
.table tbody tr:hover { background: #f7fafd; }
.table .row-group td {
  background: #eef2f7;
  color: var(--ink-soft);
  font-weight: 700;
  text-align: left;
  font-size: 0.85rem;
}
.table .row-ours { background: var(--hkust-gold-soft) !important; }
.table .row-ours td { color: var(--hkust-blue-700); }
.table .row-ours:hover { background: #e3d7bb !important; }

/* ---------- Code / BibTeX ---------- */
.code {
  background: #0d2540;
  color: #e7eef6;
  border-radius: var(--radius-sm);
  padding: 18px 20px;
  overflow-x: auto;
  font-size: 0.86rem;
  line-height: 1.55;
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
}

/* ---------- Footer ---------- */
.footer { background: var(--hkust-blue); color: #cfe0f0; padding: 28px 0; }
.footer a { color: #ffd98a; }
.footer .muted { color: #aac4dd; }
.footer__inner { display: flex; flex-direction: column; gap: 4px; }

/* ---------- Lightbox ---------- */
.lightbox {
  position: fixed;
  inset: 0;
  z-index: 1000;
  display: none;
  align-items: center;
  justify-content: center;
  padding: 32px;
}
.lightbox.is-open { display: flex; }
.lightbox__backdrop {
  position: absolute;
  inset: 0;
  background: rgba(6, 18, 33, 0.86);
  border: none;
  cursor: zoom-out;
}
.lightbox__figure {
  position: relative;
  margin: 0;
  max-width: 94vw;
  max-height: 92vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 10px;
}
.lightbox__img {
  max-width: 94vw;
  max-height: 84vh;
  border-radius: 10px;
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.5);
  background: #fff;
}
.lightbox__caption { color: #d8e4f0; max-width: 900px; text-align: center; }
.lightbox__close {
  position: absolute;
  top: -14px;
  right: -14px;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  border: none;
  background: #fff;
  color: var(--hkust-blue);
  font-size: 1.5rem;
  line-height: 1;
  cursor: pointer;
  box-shadow: var(--shadow-lg);
}

/* ---------- Responsive ---------- */
@media (max-width: 900px) {
  .grid--4 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .hero__title--big { font-size: 3rem; }
  .hero__subtitle { font-size: 1.2rem; }
  .nav { display: none; }
}
@media (max-width: 640px) {
  .grid--2, .grid--4 { grid-template-columns: 1fr; }
  .section { padding: 44px 0; }
  .section h2 { font-size: 1.6rem; }
  .hero__title--big { font-size: 2.4rem; }
  .partnerLogos__img { height: 30px; }
  .topbar__inner { gap: 10px; }
}