:root {
  color-scheme: light;
  --paper: #f3f5f2;
  --ink: #173d35;
  --muted: #455f55;
  --line: #d6e0d8;
  --accent: #237260;
  font-family: system-ui, sans-serif;
  line-height: 1.55;
}

*, *::before, *::after { box-sizing: border-box; }
body { margin: 0; color: var(--ink); background: var(--paper); }
h1, h2, h3, p { margin: 0; }
a { color: inherit; text-underline-offset: .24em; }
a:focus-visible { outline: 3px solid #12679e; outline-offset: 4px; }
.wrap { width: min(72rem, calc(100% - 3rem)); margin-inline: auto; }

.skip-link {
  position: absolute;
  top: .75rem;
  left: .75rem;
  z-index: 1;
  padding: .6rem .9rem;
  background: white;
  transform: translateY(-200%);
}

.skip-link:focus { transform: translateY(0); }
.site-header { background: white; border-bottom: 1px solid var(--line); }
.masthead {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
  padding-block: 1.15rem;
  border-bottom: 1px solid var(--line);
}

.masthead span { color: var(--muted); font-size: .875rem; }
.brand { font-weight: 800; letter-spacing: .12em; text-decoration: none; }
.main-nav {
  display: grid;
  grid-template-columns: repeat(6, minmax(0, 1fr));
  gap: .4rem;
  margin: 0;
  padding: .45rem 0;
  list-style: none;
}

.main-nav a {
  display: block;
  padding: .65rem .45rem;
  border-radius: .35rem;
  font-size: .875rem;
  font-weight: 650;
  text-align: center;
  text-decoration: none;
}

.main-nav a:hover { background: #eaf2ed; text-decoration: underline; }

.hero {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(14rem, .4fr);
  align-items: center;
  gap: clamp(1.5rem, 5vw, 4.5rem);
  margin-block: clamp(1rem, 4vw, 3rem);
  padding: clamp(1.3rem, 5vw, 3.75rem);
  border-radius: 1.25rem;
  background: var(--ink);
  color: white;
}

.eyebrow { color: #c0e5ce; font-size: .75rem; font-weight: 700; letter-spacing: .14em; }
.hero h1 {
  margin-block: .35rem .65rem;
  font-size: clamp(2rem, 5.5vw, 4.3rem);
  line-height: 1.07;
  letter-spacing: -.045em;
}

.hero p:last-child { max-width: 50ch; color: #e5f0e9; }
.lab-link {
  display: grid;
  gap: .15rem;
  align-content: center;
  min-height: 8rem;
  padding: 1rem 1.25rem;
  border: 1px solid #81ad96;
  border-radius: .8rem;
  text-decoration: none;
}

.lab-link:hover { background: #255346; }
.lab-link:focus-visible { outline-color: white; }
.lab-link > span:first-child { color: #c0e5ce; font-size: .8rem; }
.lab-link strong { font-size: 1.35rem; }
.link-label { margin-top: .4rem; font-size: .9rem; text-decoration: underline; }
.levels h2 { margin-bottom: 1rem; font-size: 1.55rem; }
.category-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: .9rem; }
.category {
  padding: 1.15rem 1.25rem 1.25rem;
  border: 1px solid var(--line);
  border-radius: .8rem;
  background: white;
  scroll-margin-top: 1rem;
}

.category:target { border-color: var(--accent); box-shadow: inset 0 0 0 1px var(--accent); }
.category-number { color: var(--accent); font-size: .8rem; font-weight: 700; letter-spacing: .08em; }
.category h3 { margin-block: .3rem; font-size: 1.1rem; }
.category p { color: var(--muted); font-size: .93rem; }
.category-link { display: inline-block; margin-top: .65rem; color: var(--accent); font-size: .86rem; font-weight: 650; }
.site-footer {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: .75rem;
  margin-top: 2.5rem;
  padding-block: 1rem 1.5rem;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: .85rem;
}

@media (max-width: 50rem) {
  .main-nav { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .category-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

@media (max-width: 37rem) {
  .wrap { width: calc(100% - 2rem); }
  .main-nav { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .main-nav a { text-align: left; }
  .hero, .category-grid { grid-template-columns: 1fr; }
}