:root {
  --bg: #ffffff;
  --bg-alt: #f6f8fa;
  --text: #1e1e1e;
  --muted: #93a1ad; /* SEAS Grey */
  --primary: #A51C30; /* Harvard Crimson */
  --primary-600: #821627; /* Darker Crimson for hover */
  --border: rgba(147, 161, 173, 0.45); /* SEAS Grey @ 45% for subtle borders */
  --card: #ffffff;
}

* { box-sizing: border-box; }
html { color-scheme: light; }
body {
  margin: 0;
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Ubuntu, Cantarell, Noto Sans, Helvetica, Arial, "Apple Color Emoji", "Segoe UI Emoji";
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
}

img { max-width: 100%; display: block; }
a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }

.container {
  width: min(1100px, 92%);
  margin-inline: auto;
}

.section { padding: 3.25rem 0; }
.section .container > :last-child { margin-bottom: 0; }
@media (min-width: 900px) { .section { padding: 4.5rem 0; } }

/* Improve anchor navigation with sticky header */
section[id] { scroll-margin-top: 80px; }
.section--alt { background: var(--bg-alt); }

.site-header { position: sticky; top: 0; z-index: 100; background: var(--bg); border-bottom: 1px solid var(--border); }
.nav { display: flex; align-items: center; justify-content: space-between; padding: 1rem 0; }
.nav__brand { display: inline-flex; align-items: center; gap: .6rem; font-weight: 700; color: var(--text); }
.nav__logo { font-size: 1.3rem; }
.nav__menu { display: flex; align-items: center; gap: 1rem; }
.nav__menu a { color: var(--text); opacity: .9; }
.nav__menu a:hover { opacity: 1; }
.nav__toggle { display: none; }
.nav__hamburger { display: none; cursor: pointer; }

@media (max-width: 800px) {
  .nav__hamburger { display: block; }
  .nav__menu { display: none; position: absolute; right: 4%; top: 56px; background: var(--card); border: 1px solid var(--border); padding: .75rem; border-radius: .5rem; flex-direction: column; width: min(260px, 92%); }
  .nav__toggle:checked ~ .nav__hamburger { }
  .nav__toggle:checked ~ .nav__menu { display: flex; }
}

.notice { border-top: 1px solid var(--border); border-bottom: 1px solid var(--border); background: var(--bg-alt); padding: .65rem 0; font-size: .95rem; color: var(--muted); }

.hero { padding: 4.25rem 0 3.25rem; background: radial-gradient(1200px 500px at 50% -20%, rgba(165,28,48,.08), transparent 60%); border-bottom: 1px solid var(--border); }
@media (min-width: 900px) { .hero { padding: 5rem 0 4rem; } }
.hero__title { font-size: clamp(1.8rem, 3.5vw, 3rem); margin: 0 0 .5rem; }
.hero__tagline { margin: 0 0 .75rem; color: var(--muted); }
.hero__meta { color: var(--muted); margin-bottom: 1.25rem; }
.hero__cta { display: flex; gap: .75rem; flex-wrap: wrap; }

.btn { display: inline-block; padding: .6rem .95rem; border-radius: .55rem; background: var(--bg-alt); border: 1px solid var(--border); color: var(--text); font-weight: 600; }
.btn:hover { text-decoration: none; background: #eef2f6; }
.btn--primary { background: var(--primary); border-color: var(--primary); color: #ffffff; }
.btn--primary:hover { background: var(--primary-600); }
.btn--small { padding: .45rem .7rem; font-size: .9rem; }

.key-dates { margin: .5rem 0 0; padding-left: 1.1rem; }
.key-dates li { margin: .4rem 0; }

.grid { display: grid; gap: 1.25rem; grid-template-columns: repeat(3, minmax(0,1fr)); }
@media (max-width: 900px) { .grid { grid-template-columns: repeat(2, minmax(0,1fr)); } }
@media (max-width: 600px) { .grid { grid-template-columns: 1fr; } }

.card { background: var(--card); border: 1px solid var(--border); border-radius: .75rem; padding: 1rem; }
.card__title { margin: .25rem 0 0; font-size: 1.1rem; }
.card__subtitle { margin: .25rem 0 0; color: var(--muted); }
.avatar { width: 64px; height: 64px; border-radius: 999px; display: grid; place-items: center; background: #f0f2f5; border: 1px solid var(--border); font-size: 1.5rem; }

.schedule { display: grid; gap: .75rem; }
.slot { display: grid; grid-template-columns: 110px 1fr; gap: 1rem; align-items: start; padding: 1rem; background: var(--card); border: 1px solid var(--border); border-radius: .5rem; }
.slot__time { font-variant-numeric: tabular-nums; color: var(--muted); }

.site-footer { border-top: 1px solid var(--border); margin-top: 3rem; }
.footer__grid { display: grid; gap: 1.25rem; grid-template-columns: repeat(3, minmax(0,1fr)); padding: 2.5rem 0; }
.footer__title { margin: 0 0 .5rem; }
.footer__links { margin: 0; padding-left: 1rem; }
.footer__bottom { border-top: 1px solid var(--border); color: var(--muted); padding: .75rem 0; }

/* Headings rhythm */
h1 { margin: 0 0 1rem; }
h2 { margin: 0 0 .85rem; }
h3 { margin: 0 0 .65rem; }

/* Accessibility helpers */
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border-width: 0; }