/* --- Tokens --- */
:root {
  --bg: #ffffff;
  --bg-soft: #f7f7f9;
  --ink: #1a1a1f;
  --ink-soft: #4b5563;
  --ink-muted: #6b7280;
  --border: #e5e7eb;
  --accent: #2b3a67;
  --accent-soft: #e8ecf7;
  --code-bg: #0f1222;
  --code-ink: #e6e8f2;
  --radius: 10px;
  --content-width: 880px;
  --shadow-sm: 0 1px 2px rgba(15, 18, 34, 0.04), 0 1px 3px rgba(15, 18, 34, 0.06);

  --font-sans: "Inter", ui-sans-serif, system-ui, -apple-system, "Segoe UI",
    Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-serif: "Source Serif 4", ui-serif, Georgia, Cambria, "Times New Roman",
    Times, serif;
  --font-mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas,
    "Liberation Mono", monospace;
}

/* Dark tokens — applied explicitly via [data-theme="dark"]
   OR automatically when OS prefers dark AND user hasn't forced light. */
:root[data-theme="dark"] {
  --bg: #0e1015;
  --bg-soft: #15181f;
  --ink: #eef1f6;
  --ink-soft: #b8bec9;
  --ink-muted: #8a90a0;
  --border: #272b35;
  --accent: #9db0ee;
  --accent-soft: #1a2140;
  --code-bg: #0a0c18;
  --code-ink: #d8dbe8;
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.4);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0e1015;
    --bg-soft: #15181f;
    --ink: #eef1f6;
    --ink-soft: #b8bec9;
    --ink-muted: #8a90a0;
    --border: #272b35;
    --accent: #9db0ee;
    --accent-soft: #1a2140;
    --code-bg: #0a0c18;
    --code-ink: #d8dbe8;
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.4);
  }
}

/* --- Reset --- */
*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 72px; }
body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: 17px;
  line-height: 1.65;
  color: var(--ink);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}
a { color: var(--accent); text-decoration-thickness: 1px; text-underline-offset: 3px; }
a:hover { text-decoration-thickness: 2px; }

/* --- Skip link --- */
.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--ink);
  color: var(--bg);
  padding: 8px 14px;
  z-index: 1000;
}
.skip-link:focus { left: 8px; top: 8px; }

/* --- Header / nav --- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: color-mix(in srgb, var(--bg) 92%, transparent);
  backdrop-filter: saturate(140%) blur(10px);
  -webkit-backdrop-filter: saturate(140%) blur(10px);
  border-bottom: 1px solid var(--border);
}
.nav {
  max-width: var(--content-width);
  margin: 0 auto;
  padding: 14px 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}
.nav-brand {
  font-weight: 700;
  color: var(--ink);
  text-decoration: none;
  letter-spacing: -0.01em;
}
.nav-right {
  display: flex;
  align-items: center;
  gap: 18px;
}
.nav-links {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  gap: 22px;
}
.nav-links a {
  color: var(--ink-soft);
  text-decoration: none;
  font-size: 15px;
}
.nav-links a:hover { color: var(--accent); }
.nav-toggle {
  display: none;
  background: none;
  border: 0;
  cursor: pointer;
  padding: 6px;
  flex-direction: column;
  gap: 4px;
}
.nav-toggle span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--ink);
  border-radius: 2px;
}

/* --- Theme toggle --- */
.theme-toggle {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--bg);
  color: var(--ink-soft);
  cursor: pointer;
  padding: 0;
  transition: color 0.15s ease, background 0.15s ease, border-color 0.15s ease;
}
.theme-toggle:hover {
  color: var(--accent);
  border-color: color-mix(in srgb, var(--accent) 40%, var(--border));
  background: var(--bg-soft);
}
.theme-toggle:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}
.theme-toggle .icon { display: block; }
/* Default (light effective): show moon, hide sun */
.theme-toggle .icon-sun { display: none; }
.theme-toggle .icon-moon { display: block; }
/* Dark effective: show sun, hide moon */
:root[data-theme="dark"] .theme-toggle .icon-sun { display: block; }
:root[data-theme="dark"] .theme-toggle .icon-moon { display: none; }
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) .theme-toggle .icon-sun { display: block; }
  :root:not([data-theme="light"]) .theme-toggle .icon-moon { display: none; }
}

@media (max-width: 680px) {
  .nav-toggle { display: flex; }
  .nav-right { gap: 8px; }
  .nav-links {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    flex-direction: column;
    gap: 0;
    background: var(--bg);
    border-bottom: 1px solid var(--border);
    padding: 8px 0;
  }
  .nav-links.open { display: flex; }
  .nav-links li { padding: 0; }
  .nav-links a {
    display: block;
    padding: 12px 24px;
  }
}

/* --- Main layout --- */
main {
  max-width: var(--content-width);
  margin: 0 auto;
  padding: 0 24px;
}
.section {
  padding: 56px 0;
  border-top: 1px solid var(--border);
}

h1, h2, h3, h4 {
  font-family: var(--font-serif);
  color: var(--ink);
  letter-spacing: -0.015em;
  line-height: 1.2;
  margin: 0 0 0.5em;
}
h2 {
  font-size: 1.9rem;
  margin-bottom: 0.75em;
}
h3 { font-size: 1.3rem; }
h4 { font-size: 1.05rem; font-family: var(--font-sans); font-weight: 600; }
p { margin: 0 0 1em; }
.section-intro { color: var(--ink-soft); margin-bottom: 1.75em; }

/* --- Hero --- */
.hero {
  padding: 72px 0 48px;
  text-align: left;
}
.venue-badge {
  display: inline-block;
  background: var(--accent-soft);
  color: var(--accent);
  border: 1px solid color-mix(in srgb, var(--accent) 18%, transparent);
  border-radius: 999px;
  padding: 6px 14px;
  font-size: 14px;
  font-weight: 500;
  margin: 0 8px 24px 0;
}
.venue-badge--alt {
  --alt-accent: #8a4b2b;
  background: color-mix(in srgb, var(--alt-accent) 10%, transparent);
  color: var(--alt-accent);
  border-color: color-mix(in srgb, var(--alt-accent) 22%, transparent);
}
:root[data-theme="dark"] .venue-badge--alt,
:root:not([data-theme="light"]) .venue-badge--alt {
  --alt-accent: #eebf9d;
}
.hero h1 {
  font-size: clamp(2.1rem, 4.6vw, 3.2rem);
  margin: 0 0 16px;
}
.accent { color: var(--accent); }
.tagline {
  font-size: 1.15rem;
  color: var(--ink-soft);
  max-width: 640px;
  margin: 0;
}

/* --- Outline --- */
.outline {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: 28px;
}
.outline-part {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px 26px;
  background: var(--bg-soft);
}
.outline-head {
  display: flex;
  align-items: baseline;
  flex-wrap: wrap;
  gap: 10px 16px;
  margin-bottom: 8px;
}
.outline-num {
  font-size: 12px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--accent);
  background: var(--accent-soft);
  padding: 3px 10px;
  border-radius: 999px;
}
.outline-head h3 { margin: 0; flex: 1 1 auto; }
.outline-meta {
  font-size: 13px;
  color: var(--ink-muted);
  font-variant-numeric: tabular-nums;
}
.outline-leads {
  font-size: 14px;
  color: var(--ink-muted);
  margin: 0 0 10px;
}
.outline-leads .label {
  text-transform: uppercase;
  letter-spacing: 0.06em;
  font-size: 11px;
  font-weight: 700;
  margin-right: 6px;
}
.outline-sub {
  margin-top: 20px;
  padding-top: 16px;
  border-top: 1px dashed var(--border);
}
.outline-sub h4 {
  display: flex;
  align-items: baseline;
  gap: 12px;
  justify-content: space-between;
}
.outline-break {
  text-align: center;
  font-size: 14px;
  color: var(--ink-muted);
  margin: 20px 0 0;
  padding: 10px 0;
  border-top: 1px dashed var(--border);
  border-bottom: 1px dashed var(--border);
}

/* --- Speakers --- */
.speakers {
  list-style: none;
  padding: 0;
  margin: 0;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 20px;
}
.speaker {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 22px 20px;
  background: var(--bg-soft);
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}
.speaker:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-sm);
}
.speaker-photo {
  width: 104px;
  height: 104px;
  border-radius: 50%;
  object-fit: cover;
  display: block;
  margin: 0 0 16px;
  border: 2px solid var(--border);
  background: var(--bg-soft);
}
.speaker h3 {
  font-family: var(--font-sans);
  font-size: 1.05rem;
  font-weight: 600;
  margin: 0 0 4px;
}
.speaker .affil {
  font-size: 14px;
  color: var(--ink-soft);
  margin: 0;
}

/* --- Materials --- */
.materials {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.materials li {
  padding: 14px 18px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--bg-soft);
}

/* --- BibTeX block --- */
.bibtex {
  background: var(--code-bg);
  color: var(--code-ink);
  border-radius: var(--radius);
  padding: 20px 22px;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 13.5px;
  line-height: 1.6;
  margin: 0;
}
.bibtex code { font-family: inherit; }

/* --- Footer --- */
.site-footer {
  max-width: var(--content-width);
  margin: 40px auto 0;
  padding: 28px 24px 40px;
  border-top: 1px solid var(--border);
  color: var(--ink-muted);
  font-size: 14px;
}
.site-footer a { color: var(--ink-soft); }
.site-footer .fine { margin-top: 6px; color: var(--ink-muted); font-size: 13px; }

/* --- Selection --- */
::selection { background: var(--accent-soft); color: var(--accent); }