:root {
  color-scheme: light;
  --ink: #182820;
  --muted: #617168;
  --line: #dce4de;
  --paper: #f6f8f5;
  --card: #ffffff;
  --accent: #107044;
  --tint: #e8f2eb;
  --radius: 12px;
  --width: 64rem;
}

* { box-sizing: border-box; }
body { margin: 0; background: var(--paper); color: var(--ink); font: 16px/1.65 system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif; }
a { color: var(--accent); text-underline-offset: .2em; }
button, input { font: inherit; }
:where(a, button, input):focus-visible { outline: 3px solid var(--accent); outline-offset: 4px; }
[hidden] { display: none !important; }
[id] { scroll-margin-top: 6rem; }
.skip-link { position: fixed; top: -5rem; left: 1rem; z-index: 20; background: var(--card); padding: .6rem 1rem; }
.skip-link:focus { top: .5rem; }

/* Shared site navigation */
.site-header { position: sticky; top: 0; z-index: 10; background: var(--card); border-bottom: 1px solid var(--line); }
.navbar { width: min(var(--width), calc(100% - 3rem)); min-height: 76px; margin: auto; display: flex; align-items: center; justify-content: space-between; gap: 2rem; }
.brand { display: inline-flex; align-items: center; gap: .65rem; color: var(--ink); font-size: 1.15rem; font-weight: 750; letter-spacing: -.03em; text-decoration: none; }
.brand svg { width: 30px; height: 30px; color: var(--accent); }
.nav-links { display: flex; gap: .35rem; }
.nav-links a { padding: .5rem 1rem; border-radius: 8px; color: var(--muted); text-decoration: none; font-size: .95rem; font-weight: 600; }
.nav-links a:hover { background: var(--paper); color: var(--ink); }
.nav-links a[aria-current="page"] { background: var(--tint); color: var(--accent); }

main { width: min(var(--width), calc(100% - 3rem)); margin: auto; padding: 3.5rem 0; }
.page-header { padding-bottom: 2rem; border-bottom: 1px solid var(--line); }
h1, h2, h3 { line-height: 1.2; }
h1 { margin: 0; max-width: 18ch; font-size: clamp(2.4rem, 5vw, 3.6rem); font-weight: 750; letter-spacing: -.045em; }
h2 { margin: 0 0 1rem; font-size: clamp(1.6rem, 3vw, 2.1rem); letter-spacing: -.025em; }
h3 { margin: 0; font-size: 1.15rem; letter-spacing: -.015em; }
.page-header > p { max-width: 44rem; margin: 1rem 0 0; color: var(--muted); font-size: 1.05rem; }
.count, #count { color: var(--muted); font-size: .9rem; }
footer { padding-top: 2rem; color: var(--muted); font-size: .9rem; }
iframe { display: block; width: 100%; aspect-ratio: 16 / 9; border: 0; background: #111; }

/* Ladder outline and lessons */
.index { padding: 2rem 0; border-bottom: 1px solid var(--line); }
.index h2 { font-size: 1.35rem; }
.index-grid { max-width: 48rem; }
.index-grid > section + section { margin-top: 1.2rem; }
.index h3 { margin-bottom: .35rem; font-size: 1rem; }
.index ol { margin: .35rem 0 0 1rem; padding-left: 1.15rem; }
.index li + li { margin-top: .2rem; }
.index a { text-decoration: none; }
.index a:hover { text-decoration: underline; }
.level { padding: 2.5rem 0; border-bottom: 1px solid var(--line); }
.level > h2 { margin-bottom: .4rem; }
.level > .count { margin: 0 0 1.25rem; }
.items { display: grid; gap: 1rem; }
.ladder-page article { position: relative; padding: 1.5rem 1.5rem 1.5rem 4.5rem; border: 1px solid var(--line); border-radius: var(--radius); background: var(--card); }
.number { display: grid; place-items: center; flex-shrink: 0; width: 2rem; height: 2rem; color: var(--accent); background: var(--tint); border-radius: 7px; font-size: .8rem; font-weight: 700; font-variant-numeric: tabular-nums; }
.ladder-page .number { position: absolute; top: 1.4rem; left: 1.25rem; }
article a { color: inherit; text-decoration: none; }
article a:hover { color: var(--accent); text-decoration: underline; }
article p { margin: .85rem 0 0; }
.refs { color: var(--accent); font-weight: 600; }
.video-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 1rem; margin-top: 1rem; }
.video-embed { margin: 0; overflow: hidden; border: 1px solid var(--line); border-radius: 8px; background: var(--paper); }
.video-embed figcaption { padding: .65rem .8rem; font-size: .9rem; font-weight: 650; }
.video-slot { position: relative; aspect-ratio: 16 / 9; background: #111; }
.video-slot > img, .video-slot > iframe { position: absolute; inset: 0; display: block; width: 100%; height: 100%; }
.video-slot > img { object-fit: cover; }

/* Video library */
.filters { display: flex; flex-wrap: wrap; gap: .5rem; margin-top: 1.75rem; }
.filters button { padding: .5rem 1rem; border: 1px solid var(--line); background: var(--card); color: var(--muted); border-radius: 8px; cursor: pointer; font-size: .9rem; font-weight: 600; }
.filters button:hover { color: var(--accent); border-color: var(--accent); }
.filters button[aria-pressed="true"] { background: var(--accent); border-color: var(--accent); color: white; }
.search { display: block; margin-top: 1.5rem; font-size: .9rem; font-weight: 650; }
input { display: block; width: 100%; margin-top: .5rem; padding: .75rem 1rem; border: 1px solid var(--line); border-radius: 8px; color: var(--ink); background: var(--card); }
.page-header #count { margin-top: 1rem; font-size: .9rem; }
#videos { display: grid; gap: 1rem; list-style: none; margin: 1.5rem 0 0; padding: 0; }
.video { display: flex; gap: 1.25rem; padding: 1.5rem; border: 1px solid var(--line); border-radius: var(--radius); background: var(--card); }
.entry { flex: 1; min-width: 0; }
.video h2 { margin: 0 0 .35rem; font-size: 1.15rem; letter-spacing: -.015em; }
.difficulty { margin: 0; color: var(--muted); font-size: .85rem; }
.video iframe { margin-top: 1rem; border-radius: 8px; }
.videos-page footer { margin-top: 2rem; border-top: 1px solid var(--line); }
.pagination { display: flex; align-items: center; justify-content: space-between; gap: .75rem; margin-top: 1.5rem; font-size: .9rem; }
.pagination button, .pagination select { padding: .5rem .75rem; border: 1px solid var(--line); border-radius: 8px; background: var(--card); color: var(--ink); font: inherit; }
.pagination button { cursor: pointer; font-weight: 600; }
.pagination button:hover:not(:disabled) { border-color: var(--accent); color: var(--accent); }
.pagination button:disabled { opacity: .45; cursor: default; }
.pagination select { margin-left: .3rem; }
#empty-results { padding: 2rem 0; color: var(--muted); }

@media (max-width: 42rem) {
  .navbar, main { width: calc(100% - 2rem); }
  .navbar { min-height: 66px; gap: 1rem; }
  .nav-links a { padding: .45rem .7rem; }
  main { padding: 2rem 0; }
  .ladder-page article { padding: 4.25rem 1rem 1.25rem; }
  .ladder-page .number { top: 1rem; left: 1rem; }
  .video-grid { grid-template-columns: 1fr; }
  .video { padding: 1rem; gap: .75rem; }
}
@media print {
  @page { margin: 12mm; }
  body { background: #fff; font-size: 10pt; }
  .site-header, .skip-link, .filters, .search, .pagination, iframe, .video-grid, footer { display: none; }
  main { width: 100%; padding: 0; }
  .page-header { padding-bottom: 6mm; }
  h1 { font-size: 28pt; }
  h2 { font-size: 18pt; }
  h3 { font-size: 12pt; }
  .level, .index { padding: 6mm 0; }
  article, .video { break-inside: avoid; }
  [id] { scroll-margin-top: 0; }
}