:root {
  --bg: #ffffff;
  --bg-alt: #f5f7f9;
  --surface: #ffffff;
  --text: #1b2430;
  --muted: #5b6776;
  --border: #e1e6ec;
  --accent: #0f6e72;
  --accent-strong: #0a5357;
  --accent-soft: #e3f1f1;
  --on-accent: #ffffff;
  --shadow: 0 1px 2px rgba(16, 24, 40, .05), 0 4px 12px rgba(16, 24, 40, .04);
  --radius: 10px;
  --logo-bg: #ffffff;           /* logo strip is white in both themes */
  --logo-muted: #5b6776;
  --tl-track: #dfe5ea;
  --tl-future: #c4ccd4;
  --tl-faint: #9aa4b0;
  --tl-halo: rgba(15, 110, 114, .25);
  --font-sans: "Inter", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --font-serif: "Source Serif 4", Georgia, serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #11161c;
    --bg-alt: #161d25;
    --surface: #1b232d;
    --text: #e6ebf0;
    --muted: #9aa6b4;
    --border: #2a3440;
    --accent: #4fb9bc;
    --accent-strong: #7fd0d2;
    --accent-soft: #19363a;
    --on-accent: #0b1215;
    --shadow: none;
    --logo-bg: #ffffff;
    --tl-track: #2a3440;
    --tl-future: #4a5663;
    --tl-faint: #6f7b89;
    --tl-halo: rgba(79, 185, 188, .3);
  }
}

*, *::before, *::after { box-sizing: border-box; }

html { scroll-behavior: smooth; scroll-padding-top: 72px; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-sans);
  font-size: 17px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--accent); text-decoration-thickness: 1px; text-underline-offset: 2px; }
a:hover { color: var(--accent-strong); }

h1, h2, h3 { line-height: 1.25; margin: 0 0 .6em; }
h2 { font-family: var(--font-serif); font-size: 2rem; font-weight: 700; }
h3 { font-size: 1.05rem; font-weight: 600; }
p { margin: 0 0 1em; }

.container { max-width: 1100px; margin: 0 auto; padding: 0 16px; }
.narrow { max-width: 780px; }
.muted, .tba { color: var(--muted); }
.tba { font-size: .85em; font-weight: 400; }

/* ---- Navigation ---- */
.nav {
  position: sticky; top: 0; z-index: 10;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border);
}
.nav__inner { display: flex; align-items: center; justify-content: space-between; height: 60px; }
.nav__brand { display: flex; align-items: center; gap: .6rem; color: var(--text); text-decoration: none; }
.nav__mark { display: block; width: 34px; height: 34px; }
.nav__wordmark { display: block; height: 26px; width: auto; }
.nav__links { display: flex; gap: 1.4rem; }
.nav__links a { color: var(--muted); text-decoration: none; font-size: .92rem; font-weight: 500; }
.nav__links a:hover { color: var(--accent); }
.nav__toggle, .nav__burger { display: none; }

@media (max-width: 900px) {
  .nav__burger {
    display: block; width: 28px; height: 20px; position: relative; cursor: pointer;
  }
  .nav__burger span, .nav__burger::before, .nav__burger::after {
    content: ""; position: absolute; left: 0; right: 0; height: 2px; background: var(--text); border-radius: 2px;
  }
  .nav__burger::before { top: 0; }
  .nav__burger span { top: 9px; }
  .nav__burger::after { bottom: 0; }
  .nav__links {
    display: none; position: absolute; top: 60px; left: 0; right: 0;
    flex-direction: column; gap: 0; background: var(--bg); border-bottom: 1px solid var(--border);
  }
  .nav__links a { padding: .8rem 16px; border-top: 1px solid var(--border); }
  .nav__toggle:checked ~ .nav__links { display: flex; }
}

/* ---- Hero ---- */
.hero {
  padding: 6rem 0 5rem;
  background:
    radial-gradient(1200px 400px at 85% -10%, var(--accent-soft), transparent 70%),
    var(--bg);
  border-bottom: 1px solid var(--border);
}
.hero__logo { margin: 0 0 1.2rem -15px; line-height: 0; }
.hero__lockup { display: block; width: 100%; max-width: 480px; height: auto; }
.hero__meta {
  color: var(--accent); font-weight: 600; font-size: .9rem;
  text-transform: uppercase; letter-spacing: .1em; margin-bottom: 1rem;
}
.hero__lead { font-size: 1.2rem; color: var(--muted); max-width: 60ch; margin-bottom: 2rem; }
.hero__actions { display: flex; flex-wrap: wrap; gap: .8rem; }

.btn {
  display: inline-block; padding: .65rem 1.25rem; border-radius: 8px;
  border: 1px solid var(--border); background: var(--surface); color: var(--text);
  font-weight: 600; font-size: .95rem; text-decoration: none;
}
.btn:hover { border-color: var(--accent); color: var(--accent); }
.btn--primary { background: var(--accent); border-color: var(--accent); color: var(--on-accent); }
.btn--primary:hover { background: var(--accent-strong); border-color: var(--accent-strong); color: var(--on-accent); }

/* ---- Sections ---- */
.section { padding: 4.5rem 0; }
.section--alt { background: var(--bg-alt); border-top: 1px solid var(--border); border-bottom: 1px solid var(--border); }

/* Topic cards */
.cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(250px, 1fr)); gap: 1rem; }
.card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 1.3rem 1.4rem; box-shadow: var(--shadow); border-top: 3px solid var(--accent);
}
.card p { color: var(--muted); font-size: .95rem; margin: 0; }

/* Submission tracks */
.tracks { list-style: none; counter-reset: track; padding: 0; margin: 1.5rem 0 2.5rem; }
.tracks li {
  counter-increment: track; position: relative;
  padding: 0 0 1.2rem 3.2rem; margin-bottom: 1.2rem; border-bottom: 1px solid var(--border);
}
.tracks li::before {
  content: counter(track); position: absolute; left: 0; top: -.1rem;
  width: 2.1rem; height: 2.1rem; border-radius: 50%;
  background: var(--accent-soft); color: var(--accent); font-weight: 700;
  display: grid; place-items: center;
}
.tracks h3 { margin-bottom: .3em; }
.tracks p { color: var(--muted); margin: 0; }

/* Timeline */
/* Important dates: milestones joined by named stretches; the current stretch fills with elapsed time. */
.tl { list-style: none; margin: 0; padding: 0; }
.tl__row, .tl__seg { display: grid; grid-template-columns: 24px minmax(0, 1fr); column-gap: 16px; }
.tl__row { align-items: center; }
.tl__dot { justify-self: center; width: 14px; height: 14px; border-radius: 50%; background: var(--surface); border: 3px solid var(--tl-future); }
.tl__text { display: flex; align-items: baseline; flex-wrap: wrap; gap: 0 10px; }
.tl__date { font-size: 15px; font-weight: 700; color: var(--muted); white-space: nowrap; }
.tl__tz { font-size: 12px; font-weight: 500; color: var(--muted); }
.tl__label { font-size: 14px; font-weight: 500; color: var(--tl-faint); }
.tl__item--passed .tl__dot { background: var(--accent); border-color: var(--accent); }
.tl__item--passed .tl__date { color: var(--text); }
.tl__item--passed .tl__label { color: var(--muted); }
.tl__item--next .tl__dot { width: 18px; height: 18px; border-color: var(--text); }
.tl__item--next .tl__date, .tl__item--next .tl__label { color: var(--text); }
.tl__item--next .tl__label { font-weight: 700; }

.tl__seg { min-height: 96px; }
.tl__rail { position: relative; display: flex; justify-content: center; margin: 4px 0; }
.tl__track { width: 4px; border-radius: 3px; background: var(--tl-track); overflow: hidden; }
.tl__fill { height: var(--f, 0%); background: var(--accent); }
.tl__now { display: none; position: absolute; top: var(--f, 0%); left: 50%; transform: translate(-50%, -50%);
  width: 12px; height: 12px; border-radius: 50%; background: var(--text);
  box-shadow: 0 0 0 4px var(--bg-alt), 0 0 0 6px var(--tl-halo); }
.tl__segtext { display: flex; flex-direction: column; justify-content: center; align-items: flex-start; gap: 8px; padding: 10px 0; }
.tl__phase { font-size: 11px; font-weight: 600; letter-spacing: .14em; text-transform: uppercase; color: var(--tl-faint); }
.tl__today { display: none; font-size: 12px; font-weight: 600; background: var(--text); color: var(--bg-alt); padding: 4px 10px; border-radius: 999px; }
.tl__seg--past .tl__phase { color: var(--muted); }
.tl__seg--current .tl__track { width: 6px; }
.tl__seg--current .tl__now, .tl__seg--current .tl__today { display: block; }
.tl__seg--current .tl__phase { color: var(--accent); font-weight: 700; }

/* Schedule */
.schedule { width: 100%; border-collapse: collapse; margin-top: 1rem; }
.schedule th {
  text-align: left; font-size: .8rem; text-transform: uppercase; letter-spacing: .08em;
  color: var(--muted); padding: .6rem .8rem; border-bottom: 2px solid var(--border);
}
.schedule td { padding: .9rem .8rem; border-bottom: 1px solid var(--border); vertical-align: top; }
.schedule__time { white-space: nowrap; font-variant-numeric: tabular-nums; color: var(--muted); width: 8.5rem; }
.schedule__activity { font-weight: 500; }
.schedule__detail { color: var(--muted); font-size: .9rem; }
.schedule__keynote td { background: var(--accent-soft); }
.schedule__keynote .schedule__activity { color: var(--accent-strong); font-weight: 600; }

/* People */
.people { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 1.2rem; }
.person {
  display: flex; gap: 1rem; align-items: center;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 1rem 1.2rem; box-shadow: var(--shadow);
}
.person__photo { width: 72px; height: 72px; border-radius: 50%; object-fit: cover; flex-shrink: 0; }
.person__photo--img { overflow: hidden; box-shadow: 0 0 0 1px var(--border); }
.person__photo--img img { display: block; width: 100%; height: 100%; object-fit: cover; }
.person__photo--initials {
  display: grid; place-items: center; background: var(--accent-soft); color: var(--accent);
  font-weight: 700; font-size: 1.3rem; letter-spacing: .03em;
}
.person__role { font-size: .75rem; text-transform: uppercase; letter-spacing: .08em; color: var(--accent); font-weight: 600; }
.person__name { margin: 0 0 .15em; font-size: 1.05rem; }
.person__name a { color: var(--text); text-decoration: none; }
.person__name a:hover { color: var(--accent); }
.person__aff { margin: 0; color: var(--muted); font-size: .9rem; line-height: 1.45; }
.people--speakers .person__photo { width: 96px; height: 96px; }

.pc-heading { margin-top: 3.5rem; }
.pc {
  list-style: none; padding: 0; margin: 0;
  display: grid; grid-template-columns: repeat(auto-fill, minmax(320px, 1fr)); gap: .1rem 2rem;
}
.pc li { padding: .55rem 0; border-bottom: 1px solid var(--border); }
.pc__name { display: block; font-weight: 500; }
.pc__aff { display: block; color: var(--muted); font-size: .88rem; }

/* Footer */
.footer { padding: 2.5rem 0; background: var(--bg-alt); border-top: 1px solid var(--border); font-size: .88rem; color: var(--muted); }
.footer__ack { max-width: 780px; }
.footer__meta { margin: 0; }

@media (max-width: 600px) {
  body { font-size: 16px; }
  .hero { padding: 3rem 0 3.5rem; }
  .hero__logo { margin-left: -6px; }
  .section { padding: 3.2rem 0; }
  h2 { font-size: 1.65rem; }
  .people, .pc { grid-template-columns: 1fr; }
  .schedule__time { width: auto; }
}

/* The dark lockup carries its own solid background, so keep the hero flat. */
@media (prefers-color-scheme: dark) {
  .hero { background: var(--bg); }
}

/* Logo strip */
.logos { background: var(--logo-bg); border-top: 1px solid var(--border); padding: 2.5rem 0; }
.logos__title { font-family: var(--font-sans); font-size: .8rem; font-weight: 600; text-transform: uppercase; letter-spacing: .1em; color: var(--logo-muted); text-align: left; margin: 0 0 1.6rem; }
.logos__list { list-style: none; margin: 0; padding: 0; display: flex; flex-wrap: wrap; justify-content: center; align-items: center; gap: 1.4rem 1.8rem; }
.logos__list a { display: block; }
.logos__list img { display: block; height: var(--h, 44px); width: auto; max-width: 136px; object-fit: contain; }