/* Claude Learner docs — editorial minimal.
   Cool neutral surfaces, one restrained accent, a refined type scale, and
   whitespace doing the organising work that boxes used to do. */

:root {
  color-scheme: light dark;
  --bg: #ffffff;
  --fg: #14161a;
  --muted: #5b5f6b;
  --rule: #e6e6ea;
  --card: #f6f6f8;
  --code-bg: #f0f0f4;
  /* WCAG AA (4.5:1) against every surface --accent sits on as text: 5.80:1 on
     --bg, 5.37:1 on --card, 5.10:1 on --code-bg (span.hl inside a code block,
     the tightest pairing). Everywhere else it is a border or an outline, which
     carries no contrast minimum. */
  --accent: #5b52d6;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
  --measure: 43rem;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0a0a0c;
    --fg: #e7e7ea;
    --muted: #9a9ba5;
    --rule: #24242b;
    --card: #16161b;
    --code-bg: #1c1c22;
    /* 8.39:1 on --bg, 7.65:1 on --card, 7.19:1 on --code-bg — comfortably clear
       in the mode where a lighter accent has to hold up against a near-black
       page, not just where it happens to be easy. */
    --accent: #a79dff;
  }
}

*, *::before, *::after { box-sizing: border-box; }
html {
  -webkit-text-size-adjust: 100%;
  text-size-adjust: 100%;
}

body {
  margin: 0;
  padding: 3rem 1.25rem 4rem;
  background: var(--bg);
  color: var(--fg);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif;
  font-size: 1.0625rem;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}
main, footer { max-width: var(--measure); margin: 0 auto; }

::selection { background: color-mix(in srgb, var(--accent) 30%, transparent); }

/* --- type scale ------------------------------------------------------------ */

h1 {
  /* Fluid within a narrow, deliberate range rather than one fixed size —
     the same heading reads a little quieter on a phone, a little more
     confident on a wide screen, never anything in between by accident. */
  font-size: clamp(1.75rem, 1.4rem + 2.5vw, 2.375rem);
  font-weight: 700;
  line-height: 1.15;
  letter-spacing: -0.025em;
  margin: 0 0 0.75rem;
}
h2 {
  font-size: 1.4rem;
  font-weight: 600;
  line-height: 1.3;
  letter-spacing: -0.01em;
  margin: 3.5rem 0 1rem;
  padding-top: 1.9rem;
  border-top: 1px solid var(--rule);
}
h3 {
  font-size: 1.1rem;
  font-weight: 600;
  letter-spacing: -0.005em;
  margin: 2.25rem 0 0.6rem;
}
h1 + .lede {
  font-size: 1.1875rem;
  font-weight: 400;
  line-height: 1.6;
  margin: 0 0 0.9rem;
}
.sub { color: var(--muted); margin: 0 0 1.8rem; }

strong, b { font-weight: 600; }

p, ul, ol, dl { margin: 0 0 1rem; }
li { margin-bottom: 0.35rem; }
li > p { margin-bottom: 0.35rem; }
ul, ol { padding-left: 1.4rem; }

/* --- links & focus ---------------------------------------------------------- */

a {
  color: var(--accent);
  text-decoration-thickness: from-font;
  text-underline-offset: 0.15em;
  transition: text-decoration-thickness 120ms ease;
}
a:hover { text-decoration-thickness: 2px; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; border-radius: 2px; }

/* --- inline & block code ---------------------------------------------------- */

code {
  font-family: var(--mono);
  font-size: 0.875em;
  background: var(--code-bg);
  border-radius: 0.3rem;
  padding: 0.1em 0.35em;
  overflow-wrap: break-word;
}

pre {
  margin: 0 0 1.25rem;
  padding: 1rem 1.15rem;
  background: var(--code-bg);
  border: 1px solid var(--rule);
  border-radius: 0.65rem;
  overflow-x: auto;
  font-size: 0.8125rem;
  line-height: 1.65;
  tab-size: 2;
  /* Long lines wrap rather than hide: a URL or a hint comment clipped at the
     right edge of the box is content the reader silently never sees. Copying
     a wrapped line still yields the original single line. overflow-x stays
     as the backstop for anything unbreakable, so the page body never scrolls. */
  white-space: pre-wrap;
  /* anywhere, not break-word: break-word only breaks a word that would not
     fit on a line of its own, so a long URL starting mid-line still ran off
     the right edge of the box on a phone. */
  overflow-wrap: anywhere;
}
pre code {
  background: none;
  padding: 0;
  font-size: inherit;
  /* No overflow-wrap override here: it would otherwise undo the `anywhere`
     set on `pre` above (the more specific selector wins), silently
     reintroducing the long-URL overflow. overflow-x stays as the backstop
     either way. */
}

figure { margin: 0 0 1.5rem; }
figcaption {
  color: var(--muted);
  font-size: 0.8125rem;
  margin-bottom: 0.35rem;
}
/* A figcaption immediately followed by pre reads as one unit — a small
   titlebar fused to the block it names — rather than a loose label with
   air underneath it. Bare pre blocks (no caption) keep their own full,
   evenly rounded corners, so a plain shell snippet still looks complete. */
figcaption:has(+ pre) {
  background: var(--card);
  border: 1px solid var(--rule);
  border-bottom: none;
  border-radius: 0.5rem 0.5rem 0 0;
  padding: 0.5rem 1.15rem;
  margin-bottom: 0;
}
figcaption + pre { margin-top: 0; border-radius: 0 0 0.5rem 0.5rem; }

.hl { color: var(--accent); font-weight: 600; }

/* --- callouts ---------------------------------------------------------------- */

.note {
  background: var(--card);
  border-left: 2px solid var(--accent);
  border-radius: 0 0.4rem 0.4rem 0;
  padding: 0.9rem 1.15rem;
  margin: 0 0 1.4rem;
}
.note > :last-child { margin-bottom: 0; }

/* --- table of contents -------------------------------------------------------- */

.toc {
  background: var(--card);
  border: 1px solid var(--rule);
  border-radius: 0.65rem;
  padding: 1.1rem 1.4rem;
  margin-bottom: 2.5rem;
}
.toc ol {
  margin: 0;
  padding: 0;
  list-style: none;
  columns: 14rem 2;
  column-gap: 2rem;
  counter-reset: toc;
}
.toc li { counter-increment: toc; margin-bottom: 0.45rem; padding-left: 1.5rem; position: relative; }
.toc li:last-child { margin-bottom: 0; }
/* A small mono index rather than a bullet or the browser's own numeral —
   the same quiet, list-as-data feel a terminal ls -1 has. */
.toc li::before {
  content: counter(toc) ".";
  position: absolute;
  left: 0;
  color: var(--accent);
  font-family: var(--mono);
  font-size: 0.8rem;
}
.toc .toc-title {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.09em;
  color: var(--muted);
  margin: 0 0 0.7rem;
}

/* --- tables -------------------------------------------------------------------- */

/* A bordered panel, so a table too wide for a phone reads as more content to
   the right rather than as text that mysteriously stops. */
.scroll {
  overflow-x: auto;
  margin-bottom: 1.4rem;
  border: 1px solid var(--rule);
  border-radius: 0.65rem;
}
table {
  width: 100%;
  min-width: 26rem;
  border-collapse: collapse;
  font-size: 0.9rem;
  line-height: 1.5;
}
th, td {
  text-align: left;
  vertical-align: top;
  padding: 0.55rem 0.85rem;
  border-bottom: 1px solid var(--rule);
}
th {
  background: var(--card);
  font-weight: 600;
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--muted);
}
tbody tr:last-child td { border-bottom: 0; }
td code { white-space: nowrap; }
td.wrap code { white-space: normal; }

/* --- definition lists ------------------------------------------------------------ */

dt { font-weight: 600; margin-top: 1.1rem; }
dl > dt:first-child { margin-top: 0; }
dd { margin: 0.25rem 0 0; }

/* --- footer ------------------------------------------------------------------------ */

footer {
  margin-top: 3.5rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--rule);
  color: var(--muted);
  font-size: 0.9rem;
}
footer p { margin-bottom: 0.4rem; }

/* --- site chrome -------------------------------------------------------------------- */

/* The menu, on every page. Same width as main so the whole page shares one
   measure. flex-wrap so two rows are possible on a narrow viewport before
   the list itself would need to scroll. */
.site {
  max-width: var(--measure);
  margin: 0 auto 3rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--rule);
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 0.5rem 1.25rem;
}
.site .brand {
  font-weight: 700;
  letter-spacing: -0.01em;
  color: var(--fg);
  text-decoration: none;
}
.site ul {
  display: flex;
  gap: 1.1rem;
  margin: 0;
  padding: 0;
  list-style: none;
  /* A menu wider than the viewport scrolls inside itself rather than pushing
     the page body sideways — the same rule the code blocks and tables follow. */
  overflow-x: auto;
}
.site li { margin: 0; }
.site a {
  white-space: nowrap;
  color: var(--muted);
  text-decoration: none;
  font-size: 0.9375rem;
  padding-bottom: 0.4rem;
  border-bottom: 2px solid transparent;
  transition: color 120ms ease, border-color 120ms ease;
}
.site a:hover { color: var(--fg); }
/* The current page is marked by weight and a border, not by colour alone:
   colour alone is not a distinction for a reader who cannot see it. The
   border happens to be the accent — the one place on every page it is
   used purely as a wayfinding mark rather than for text. */
.site [aria-current="page"] {
  color: var(--fg);
  font-weight: 600;
  border-bottom-color: var(--accent);
}

/* The link to the next page. No border-top: the footer immediately below
   already draws one, and two rules a line apart read as a mistake. */
.next {
  margin-top: 3rem;
  color: var(--muted);
}

/* --- narrow phones ------------------------------------------------------------------- */

@media (max-width: 30em) {
  body { padding: 2.25rem 1rem 3rem; }
  h2 { margin: 2.75rem 0 0.85rem; padding-top: 1.5rem; }
  .toc { padding: 1rem 1.15rem; }
  .toc ol { columns: 1; }
  th, td { padding: 0.5rem 0.6rem; }
}