:root {
  color-scheme: light dark;
  --ww-bg: #f6f7f5;
  --ww-surface: #ffffff;
  --ww-text: #12161f;
  --ww-text-muted: #4f5b63;
  --ww-accent: #4d7c0f;
  --ww-accent-text: #3a5d0b;
  --ww-on-accent: #ffffff;
  --ww-border: #e2e5de;
  --ww-font-sans: ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto,
    "Helvetica Neue", Arial, sans-serif;
  --ww-font-mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas,
    "Liberation Mono", monospace;
  --ww-measure: 68ch;
}

* { box-sizing: border-box; }

html {
  background: var(--ww-bg);
  color: var(--ww-text);
  font-family: var(--ww-font-sans);
  font-size: 100%;
  line-height: 1.6;
  scroll-behavior: smooth;
}

body { margin: 0; min-width: 0; }
img, svg { display: block; max-width: 100%; }
button, input, select, textarea { font: inherit; }

a {
  color: var(--ww-accent-text);
  text-decoration-thickness: 0.1em;
  text-underline-offset: 0.18em;
}

a:hover { text-decoration-thickness: 0.16em; }

:focus-visible {
  outline: 3px solid var(--ww-accent-text);
  outline-offset: 3px;
}

.skip-link {
  background: var(--ww-surface);
  left: 1rem;
  padding: 0.65rem 1rem;
  position: fixed;
  top: 0.5rem;
  transform: translateY(-180%);
  z-index: 10;
}

.skip-link:focus { transform: translateY(0); }

.site-header,
.site-footer {
  border-color: var(--ww-border);
  border-style: solid;
  border-width: 0 0 1px;
}

.site-footer { border-width: 1px 0 0; color: var(--ww-text-muted); }

.shell {
  margin-inline: auto;
  max-width: 72rem;
  padding: 1rem clamp(1rem, 4vw, 2rem);
  width: 100%;
}

main.shell { padding-block: clamp(2rem, 7vw, 5rem); }

.article { max-width: var(--ww-measure); }
.brand { color: var(--ww-text); font-weight: 700; text-decoration: none; }
.lesson { overflow-wrap: break-word; }
.lesson blockquote {
  border-left: 0.3rem solid var(--ww-accent);
  margin: 1.25rem 0;
  padding: 0.25rem 0 0.25rem 1rem;
}
.lesson blockquote > :last-child { margin-bottom: 0; }
.lesson li > ol, .lesson li > ul { margin-block: 0.35rem; }
.toc { margin-block: 2rem; }
.toc h2 { margin-top: 0; }
.toc ul { columns: 2; padding-left: 1.25rem; }
.toc li { break-inside: avoid; margin-bottom: 0.35rem; }

h1, h2, h3 {
  line-height: 1.25;
  margin-block: 1.6em 0.55em;
  text-wrap: balance;
}

h1 { font-size: clamp(1.75rem, 5vw, 2.125rem); letter-spacing: -0.015em; margin-top: 0; }
h2 { font-size: 1.375rem; letter-spacing: -0.01em; }
h3 { font-size: 1.125rem; }
p, ul, ol { margin-block: 0 1em; }

.muted,
.meta,
.source-note { color: var(--ww-text-muted); }

.meta,
.source-note { font-size: 0.8125rem; letter-spacing: 0.005em; }

.card,
.prompt-block,
.output-block {
  background: var(--ww-surface);
  border: 1px solid var(--ww-border);
  border-radius: 0.75rem;
  padding: clamp(1rem, 3vw, 1.5rem);
}

.prompt-block,
.output-block {
  font-family: var(--ww-font-mono);
  overflow-wrap: anywhere;
  white-space: pre-wrap;
}

.block-label {
  color: var(--ww-text-muted);
  display: block;
  font-family: var(--ww-font-sans);
  font-size: 0.8125rem;
  font-weight: 600;
  margin-bottom: 0.5rem;
}

.button {
  align-items: center;
  background: var(--ww-accent);
  border: 2px solid var(--ww-accent);
  border-radius: 0.5rem;
  color: var(--ww-on-accent);
  cursor: pointer;
  display: inline-flex;
  font-weight: 600;
  justify-content: center;
  min-height: 44px;
  padding: 0.65rem 1rem;
  text-decoration: none;
}

.button-secondary {
  background: transparent;
  color: var(--ww-accent-text);
}

.button:hover { filter: brightness(0.92); text-decoration: none; }

.table-scroll {
  max-width: 100%;
  overflow-x: auto;
  overscroll-behavior-inline: contain;
}

table { border-collapse: collapse; min-width: 38rem; width: 100%; }
th, td { border-bottom: 1px solid var(--ww-border); padding: 0.75rem; text-align: left; }
th { background: var(--ww-surface); }

fieldset { border: 1px solid var(--ww-border); border-radius: 0.5rem; margin-block: 1rem; }
label { display: inline-flex; gap: 0.5rem; min-height: 44px; padding: 0.55rem; }
input[type="radio"], input[type="checkbox"] { inline-size: 1.25rem; block-size: 1.25rem; }

@media (prefers-color-scheme: dark) {
  :root {
    --ww-bg: #0e1117;
    --ww-surface: #161b24;
    --ww-text: #e9ecf2;
    --ww-text-muted: #a3adbd;
    --ww-accent: #a7cf5a;
    --ww-accent-text: #a7cf5a;
    --ww-on-accent: #12161f;
    --ww-border: #252c38;
  }
}

@media (max-width: 36rem) {
  .toc ul { columns: 1; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation-duration: 0.01ms !important; transition-duration: 0.01ms !important; }
}

@media print {
  :root { color-scheme: light; }
  .skip-link, nav, .button { display: none !important; }
  a { color: inherit; }
}