/* ==========================================================================
   VQC Lab — shared stylesheet
   ========================================================================== */

:root {
  --color-bg: #ffffff;
  --color-bg-alt: #f6f6fb;
  --color-bg-dark: #0f1024;
  --color-bg-dark-alt: #171933;
  --color-text: #1a1b2e;
  --color-text-muted: #5b5c72;
  --color-text-on-dark: #f1f1fb;
  --color-text-on-dark-muted: #b7b8d6;
  --color-primary: #4b3fe4;
  --color-primary-dark: #372dc4;
  --color-primary-light: #efedff;
  --color-accent: #14b8a6;
  --color-border: #e6e6f0;
  --color-border-dark: #2a2c4c;
  --font-sans: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --font-mono: "JetBrains Mono", "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
  --max-width: 1120px;
  --radius: 12px;
  --shadow-sm: 0 1px 2px rgba(20, 21, 55, 0.06), 0 1px 1px rgba(20, 21, 55, 0.04);
  --shadow-md: 0 8px 24px rgba(20, 21, 55, 0.08);
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

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

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

a {
  color: var(--color-primary);
  text-decoration: none;
}
a:hover { text-decoration: underline; }

h1, h2, h3, h4 {
  font-weight: 700;
  line-height: 1.25;
  letter-spacing: -0.01em;
  margin: 0 0 0.6em;
}

h1 { font-size: clamp(1.9rem, 3.2vw, 2.7rem); }
h2 { font-size: clamp(1.5rem, 2.4vw, 1.9rem); }
h3 { font-size: 1.15rem; }

p { margin: 0 0 1em; color: var(--color-text); }

ul { padding-left: 1.2em; }

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

.eyebrow {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-primary);
  background: var(--color-primary-light);
  padding: 4px 10px;
  border-radius: 999px;
  margin-bottom: 14px;
}

.section {
  padding: 64px 0;
}
.section--alt { background: var(--color-bg-alt); }
.section-head {
  max-width: 680px;
  margin: 0 0 36px;
}
.section-head p { color: var(--color-text-muted); }

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-weight: 600;
  font-size: 0.95rem;
  padding: 10px 20px;
  border-radius: 999px;
  border: 1px solid transparent;
  cursor: pointer;
  transition: transform 0.15s ease, box-shadow 0.15s ease, background 0.15s ease;
}
.btn:hover { text-decoration: none; }
.btn-primary {
  background: var(--color-primary);
  color: #fff;
}
.btn-primary:hover { background: var(--color-primary-dark); }
.btn-ghost {
  background: transparent;
  border-color: rgba(255, 255, 255, 0.35);
  color: var(--color-text-on-dark);
}
.btn-ghost:hover { background: rgba(255, 255, 255, 0.1); }
.btn-outline {
  background: transparent;
  border-color: var(--color-border);
  color: var(--color-text);
}
.btn-outline:hover { border-color: var(--color-primary); color: var(--color-primary); }

/* ---------- Header / Nav ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(255, 255, 255, 0.88);
  backdrop-filter: saturate(180%) blur(10px);
  border-bottom: 1px solid var(--color-border);
}
.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px 0;
}
.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 800;
  font-size: 1.15rem;
  color: var(--color-text);
}
.brand:hover { text-decoration: none; }
.brand-mark {
  width: 48px;
  height: 48px;
  display: block;
  flex-shrink: 0;
}
.brand-sub {
  display: block;
  font-size: 0.7rem;
  font-weight: 500;
  color: var(--color-text-muted);
  letter-spacing: 0.02em;
}
.nav-links {
  display: flex;
  align-items: center;
  gap: 4px;
  list-style: none;
  margin: 0;
  padding: 0;
}
.nav-links a {
  color: var(--color-text-muted);
  font-weight: 600;
  font-size: 0.92rem;
  padding: 8px 14px;
  border-radius: 8px;
}
.nav-links a:hover { color: var(--color-text); background: var(--color-bg-alt); text-decoration: none; }
.nav-links a.is-active { color: var(--color-primary); background: var(--color-primary-light); }
.nav-toggle {
  display: none;
  border: none;
  background: transparent;
  padding: 8px;
  cursor: pointer;
}
.nav-toggle span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--color-text);
  margin: 4px 0;
  border-radius: 2px;
}

@media (max-width: 800px) {
  .nav-toggle { display: block; }
  .nav-links {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background: #fff;
    border-bottom: 1px solid var(--color-border);
    flex-direction: column;
    align-items: stretch;
    padding: 8px 16px 16px;
    display: none;
  }
  .nav-links.is-open { display: flex; }
  .nav-links a { padding: 12px 8px; }
}

/* ---------- Hero ---------- */
.hero {
  position: relative;
  background: radial-gradient(1200px 600px at 15% -10%, #262a5e 0%, transparent 60%),
    linear-gradient(160deg, var(--color-bg-dark) 0%, var(--color-bg-dark-alt) 100%);
  color: var(--color-text-on-dark);
  overflow: hidden;
  padding: 96px 0 88px;
}
.hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image: radial-gradient(rgba(255, 255, 255, 0.14) 1px, transparent 1px);
  background-size: 26px 26px;
  mask-image: radial-gradient(circle at 30% 20%, black, transparent 70%);
  opacity: 0.6;
  pointer-events: none;
}
.hero-inner {
  position: relative;
  max-width: 760px;
}
.hero .eyebrow {
  background: rgba(255, 255, 255, 0.08);
  color: #cfd0ff;
}
.hero h1 { color: #fff; }
.hero p.lead {
  font-size: 1.15rem;
  color: var(--color-text-on-dark-muted);
  max-width: 620px;
}
.hero-actions {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  margin-top: 28px;
}

.page-hero {
  background: linear-gradient(160deg, var(--color-bg-dark) 0%, var(--color-bg-dark-alt) 100%);
  color: var(--color-text-on-dark);
  padding: 64px 0 56px;
}
.page-hero h1 { color: #fff; margin-bottom: 10px; }
.page-hero p { color: var(--color-text-on-dark-muted); max-width: 640px; margin: 0; }

/* ---------- Cards / Grids ---------- */
.grid {
  display: grid;
  gap: 22px;
}
.grid-3 { grid-template-columns: repeat(3, 1fr); }
.grid-2 { grid-template-columns: repeat(2, 1fr); }
@media (max-width: 900px) {
  .grid-3 { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 640px) {
  .grid-3, .grid-2 { grid-template-columns: 1fr; }
}

.card {
  background: #fff;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow-sm);
  transition: box-shadow 0.15s ease, transform 0.15s ease;
}
.card:hover { box-shadow: var(--shadow-md); transform: translateY(-2px); }
.card h3 { margin-bottom: 8px; }
.card p:last-child { margin-bottom: 0; }
a.card-link {
  display: block;
  color: inherit;
}
a.card-link:hover { text-decoration: none; }
a.card-link .link-row {
  color: var(--color-primary);
  font-weight: 600;
  align-items: center;
}
a.card-link:hover .link-row { color: var(--color-primary-dark); }
.card-icon {
  width: 40px;
  height: 40px;
  border-radius: 10px;
  background: var(--color-primary-light);
  color: var(--color-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 14px;
  font-size: 1.1rem;
}

.tag {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  padding: 3px 9px;
  border-radius: 999px;
  background: var(--color-bg-alt);
  color: var(--color-text-muted);
  border: 1px solid var(--color-border);
  margin: 0 6px 6px 0;
}
.tag-accent { color: var(--color-primary); background: var(--color-primary-light); border-color: transparent; }

.link-row { display: flex; gap: 14px; flex-wrap: wrap; margin-top: 14px; font-size: 0.9rem; }
.link-row a { display: inline-flex; align-items: center; gap: 6px; font-weight: 600; }

/* ---------- Callout box ---------- */
.callout {
  border: 1px solid var(--color-border);
  background: var(--color-primary-light);
  border-radius: var(--radius);
  padding: 24px 28px;
  display: flex;
  align-items: center;
  gap: 20px;
  flex-wrap: wrap;
  justify-content: space-between;
}
.callout p { margin: 0; color: var(--color-text); }
.callout strong { color: var(--color-primary-dark); }

/* ---------- Timeline (News) ---------- */
.timeline { list-style: none; padding: 0; margin: 0; }
.timeline-item {
  position: relative;
  padding: 0 0 34px 34px;
  border-left: 2px solid var(--color-border);
}
.timeline-item:last-child { border-color: transparent; padding-bottom: 0; }
.timeline-item::before {
  content: "";
  position: absolute;
  left: -7px;
  top: 4px;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--color-primary);
  border: 3px solid var(--color-primary-light);
}
.timeline-date {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--color-primary);
  font-weight: 700;
  letter-spacing: 0.03em;
  display: block;
  margin-bottom: 4px;
}
.timeline-item h3 { margin-bottom: 6px; font-size: 1.05rem; }
.timeline-item p { color: var(--color-text-muted); margin-bottom: 0; }
.badge-award {
  display: inline-block;
  margin-left: 8px;
  font-size: 0.72rem;
  font-weight: 700;
  color: #92400e;
  background: #fef3c7;
  padding: 2px 8px;
  border-radius: 999px;
  vertical-align: middle;
}

/* ---------- Publications ---------- */
.pub-list { list-style: none; padding: 0; margin: 0; }
.pub-item {
  padding: 20px 0;
  border-bottom: 1px solid var(--color-border);
}
.pub-item:first-child { padding-top: 0; }
.pub-item h3 { font-size: 1.05rem; margin-bottom: 6px; }
.pub-authors { color: var(--color-text-muted); margin-bottom: 6px; font-size: 0.95rem; }
.pub-authors .self { color: var(--color-text); font-weight: 700; text-decoration: underline; text-decoration-color: var(--color-border); text-underline-offset: 2px; }
.pub-venue { font-family: var(--font-mono); font-size: 0.8rem; font-weight: 700; color: var(--color-primary-dark); }
.pub-links { margin-top: 8px; display: flex; gap: 14px; flex-wrap: wrap; font-size: 0.85rem; }
.pub-links a { font-weight: 600; display: inline-flex; align-items: center; gap: 5px; }

.tabset { margin-bottom: 6px; }
.tabset input[type="radio"] { display: none; }
.tabset label {
  display: inline-block;
  padding: 8px 16px;
  margin: 0 8px 8px 0;
  border-radius: 999px;
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  color: var(--color-text-muted);
  font-size: 0.85rem;
  font-weight: 600;
  cursor: pointer;
}
.tabset input[type="radio"]:checked + label {
  background: var(--color-primary);
  border-color: var(--color-primary);
  color: #fff;
}
.publication { display: none; }
#tab1:checked ~ .pub-list .publication { display: block; }
#tab2:checked ~ .pub-list .publication[data-categories*="os"] { display: block; }
#tab3:checked ~ .pub-list .publication[data-categories*="pl"] { display: block; }
#tab4:checked ~ .pub-list .publication[data-categories*="qc"] { display: block; }
#tab5:checked ~ .pub-list .publication[data-categories*="theory"] { display: block; }

/* ---------- Team ---------- */
.person-card {
  display: flex;
  gap: 18px;
  align-items: flex-start;
}
.avatar {
  width: 84px;
  height: 84px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--color-primary), var(--color-accent));
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 1.4rem;
  flex-shrink: 0;
  font-family: var(--font-mono);
}
.person-card h3 { margin-bottom: 2px; }
.person-role { color: var(--color-primary); font-weight: 600; font-size: 0.88rem; margin-bottom: 8px; display: block; }
.person-links { display: flex; gap: 10px; margin-top: 10px; font-size: 0.85rem; }

.member-card { text-align: center; padding: 28px 20px; }
.member-card .avatar { margin: 0 auto 14px; }
.member-card h4 { margin-bottom: 2px; font-size: 1rem; }
.member-role { color: var(--color-text-muted); font-size: 0.85rem; }

.empty-slot {
  border: 1.5px dashed var(--color-border);
  border-radius: var(--radius);
  padding: 28px 20px;
  text-align: center;
  color: var(--color-text-muted);
  font-size: 0.9rem;
}

/* ---------- Footer ---------- */
.site-footer {
  background: var(--color-bg-dark);
  color: var(--color-text-on-dark-muted);
  padding: 48px 0 28px;
  margin-top: 40px;
}
.footer-grid {
  display: grid;
  grid-template-columns: 1.4fr 1fr 1fr;
  gap: 32px;
  margin-bottom: 32px;
}
@media (max-width: 700px) {
  .footer-grid { grid-template-columns: 1fr; }
}
.footer-grid h4 {
  color: #fff;
  font-size: 0.85rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  margin-bottom: 14px;
}
.footer-grid a { color: var(--color-text-on-dark-muted); }
.footer-grid a:hover { color: #fff; }
.footer-grid p { color: var(--color-text-on-dark-muted); margin-bottom: 8px; font-size: 0.92rem; }
.footer-links { list-style: none; padding: 0; margin: 0; display: flex; flex-direction: column; gap: 8px; }
.footer-icons { display: flex; gap: 14px; margin-top: 10px; font-size: 1.1rem; }
.footer-bottom {
  border-top: 1px solid var(--color-border-dark);
  padding-top: 20px;
  font-size: 0.82rem;
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 8px;
}

/* misc */
.mt-0 { margin-top: 0; }
.text-center { text-align: center; }