*,
*::before,
*::after {
  box-sizing: border-box;
}

:root {
  --nav-height: 63px; /* Fallback, updated dynamically by JS */
  --color-background: #fff;
  --color-text: #1d1d1f;
  --color-heading: #000;
  --color-muted: #86868b;
  --color-link: #000;
  --color-nav-link: #555;
  --color-nav-background: #fff;
  --color-sidebar-background: #fafafa;
  --color-code-background: #f5f5f5;
  --color-pre-background: #f6f8fa;
  --color-border: #e5e5e5;
  --color-subtle-border: #ddd;
  --color-separator: #ccc;
  --color-heading-anchor: #bbb;
  color-scheme: light dark;
}

@media (prefers-color-scheme: dark) {
  :root {
    /* Matches GitHub's dark theme canvas color (rgb(22, 27, 34)) rather than
       a near-black background. */
    --color-background: #161b22;
    --color-text: #e6e6ea;
    --color-heading: #fff;
    --color-muted: #a0a0aa;
    --color-link: #ffffff;
    --color-nav-link: #c7c7cf;
    --color-nav-background: #161b22;
    --color-sidebar-background: #161b22;
    --color-code-background: #232327;
    --color-pre-background: #0d1117;
    --color-border: #3e444c;
    --color-subtle-border: #3e444c;
    --color-separator: #3e444c;
    --color-heading-anchor: #6f6f78;
    color-scheme: dark;
  }
}

body {
  font-family: system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
  font-size: 16px;
  font-weight: 400;
  line-height: 26px;
  margin: 0;
  padding: 0;
  color: var(--color-text);
  background: var(--color-background);
  /* Break long tokens (URLs, flags, type names) instead of overflowing. */
  overflow-wrap: break-word;
}

/* Navigation */
html {
  /* Extra offset so anchor targets aren't hidden under the sticky nav. */
  scroll-padding-top: calc(var(--nav-height) + 15px);
}

.top-nav {
  background: var(--color-nav-background);
  border-bottom: 1px solid var(--color-border);
  position: sticky;
  top: 0;
  z-index: 100;
}

.nav-content {
  max-width: 900px;
  margin: 0 auto;
  padding: 1rem 1rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.5rem;
}

.nav-left {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.nav-brand {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  text-decoration: none;
  flex-shrink: 0;
}

.brand-logo {
  width: 30px;
  height: 30px;
  border-radius: 6px;
}

.nav-title {
  font-size: 18px;
  font-weight: 600;
  color: var(--color-heading);
  letter-spacing: -0.3px;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.nav-link {
  font-size: 15px;
  font-weight: 500;
  color: var(--color-nav-link);
  text-decoration: none;
  white-space: nowrap;
}

.nav-link:hover {
  color: var(--color-heading);
}

.nav-link.active {
  color: var(--color-heading);
  font-weight: 600;
}

.nav-separator {
  color: var(--color-separator);
  font-weight: 400;
}

/* Table-of-contents toggle button (shown only on mobile). */
.toc-toggle {
  display: none;
  font-family: inherit;
  font-size: 14px;
  font-weight: 600;
  color: var(--color-heading);
  background: none;
  border: 1px solid var(--color-subtle-border);
  border-radius: 6px;
  padding: 0.35rem 0.75rem;
  cursor: pointer;
}

/* Page layout: table-of-contents sidebar + content */
.page {
  display: grid;
  grid-template-columns: 280px minmax(0, 1fr);
  column-gap: 3rem;
  /* No top padding so the sidebar tucks flush under the header; flush left
     too, with a gutter kept only on the right edge. */
  padding: 0 2rem 0 0;
}

.page.no-toc {
  grid-template-columns: minmax(0, 1fr);
  max-width: 900px;
  margin: 0 auto;
  padding: 2rem;
}

/* No TOC to show, so the sidebar would otherwise render as an empty
   full-height box (it's still a grid item even with nothing in it). */
.page.no-toc .toc-sidebar {
  display: none;
}

.content {
  /* Without an explicit width, a grid item with auto margins doesn't stretch
     to fill its track - it shrinks to fit its content instead (like
     inline-block), so wide unbreakable content (e.g. long code lines) would
     blow out the layout instead of scrolling within it. */
  width: 100%;
  min-width: 0;
  max-width: 860px;
  /* Center the content within the remaining space to the right of the sidebar. */
  margin: 0 auto;
  /* Top padding lives here (not on .page) so the sidebar can reach the header. */
  padding: 2rem 0;
  /* Break long tokens (URLs, flags) instead of overflowing on narrow screens. */
  overflow-wrap: break-word;
}

/* Keep images (logo, screenshots) within the content, never spilling off. */
.content img {
  max-width: 100%;
  height: auto;
}

/* Table of contents sidebar */
.toc-sidebar {
  position: sticky;
  top: var(--nav-height);
  align-self: start;
  /* Full-height panel so the right border reads as a continuous divider. */
  min-height: calc(100vh - var(--nav-height));
  max-height: calc(100vh - var(--nav-height));
  overflow-y: auto;
  overflow-x: hidden;
  background: var(--color-sidebar-background);
  border-right: 1px solid var(--color-border);
  font-size: 14px;
  line-height: 1.5;
  /* Hide the scrollbar while keeping the sidebar scrollable. */
  scrollbar-width: none;
  -ms-overflow-style: none;
}

.toc-sidebar::-webkit-scrollbar {
  display: none;
}

.toc-sidebar #markdown-toc {
  list-style: none;
  margin: 0;
  /* A little breathing room on the left; the column gap handles the right. */
  padding: 0.75rem 0.5rem 1.5rem 1rem;
}

.toc-sidebar #markdown-toc ul {
  list-style: none;
  margin: 0;
  padding-left: 0;
}

.toc-sidebar #markdown-toc li {
  margin: 0.15rem 0;
}

.toc-sidebar #markdown-toc a {
  display: block;
  color: var(--color-nav-link);
  text-decoration: none;
  font-weight: 500;
  /* Wrap long rule names instead of scrolling the sidebar horizontally. */
  overflow-wrap: anywhere;
}

/* Bold text renders heavier on a dark background, so nested entries (e.g.
   rule names under a category) use a lighter weight than in light mode. */
@media (prefers-color-scheme: dark) {
  .toc-sidebar #markdown-toc > li > ul a {
    font-weight: 400;
  }
}

.toc-sidebar #markdown-toc a:hover {
  color: var(--color-heading);
}

/* The entry matching the current URL fragment is highlighted as selected. */
.toc-sidebar #markdown-toc a.active {
  color: var(--color-heading);
  font-weight: 700;
}

/* Top-level TOC entries stand out a little more, since they group the page
   into sections (e.g. rules.md's categories) - even ones with no nested
   sub-entries of their own (e.g. a lone "Prerelease Rules" entry). On a flat
   TOC with no categorization (e.g. index.md, tagged `toc_style: flat`),
   every entry stays the regular gray instead. */
.toc-sidebar:not(.toc-flat) > #markdown-toc > li > a {
  color: var(--color-heading);
  font-weight: 600;
}

/* Give grouped categories a bit of breathing room from the previous group,
   but not before the first one. Flat TOCs are unaffected. */
.toc-sidebar:not(.toc-flat) > #markdown-toc > li:not(:first-child) {
  margin-top: 0.75rem;
}

strong,
b {
  font-weight: 700;
}

a {
  color: var(--color-link);
  font-weight: 700;
  text-decoration-line: underline;
  text-decoration-thickness: auto;
  text-underline-offset: 2px;
}

h1 {
  color: var(--color-heading);
  font-size: 40px;
  font-weight: 700;
  line-height: 44px;
  letter-spacing: -1.2px;
}

/* Muted label under a heading (e.g. a category's "Enabled by default", or
   the homepage subtitle), set apart from regular body text so it reads as
   metadata, not content. */
.heading-note {
  margin-top: -0.75rem;
  color: var(--color-muted);
  font-size: 15px;
}

/* Disclaimer box (e.g. the /rules/develop prerelease notice). */
.callout {
  margin: 0 0 1.5rem;
  padding: 0.1rem 1.25rem;
  background: var(--color-code-background);
  border-left: 3px solid var(--color-heading);
  border-radius: 4px;
}

/* `<br/>` is used throughout the generated pages as a manual spacer (e.g.
   between rule examples, after callouts). The visible gap is dominated by
   the empty line's own line-height, not by the paragraph's margin (which
   collapses into the larger margins of neighboring elements like `pre`/`h2`
   either way) - so shrink line-height directly to make the beat smaller. */
.content p:has(> br:only-child) {
  margin: 0;
  line-height: 0.5em;
}

h2 {
  color: var(--color-heading);
  font-size: 26px;
  font-weight: 600;
  line-height: 30px;
  letter-spacing: -0.52px;
  margin-top: 2.5rem;
}

h3 {
  color: var(--color-heading);
  font-size: 22px;
  font-weight: 600;
  line-height: 26px;
  letter-spacing: -0.44px;
}

/* Heading anchors: keep the heading looking plain, reveal a `#` on hover. */
.content :is(h1, h2, h3, h4, h5, h6) .header-anchor {
  color: inherit;
  text-decoration: none;
}

.content :is(h1, h2, h3, h4, h5, h6) .header-anchor::after {
  content: " #";
  color: var(--color-heading-anchor);
  opacity: 0;
  font-weight: 400;
}

.content :is(h1, h2, h3, h4, h5, h6):hover .header-anchor::after,
.content :is(h1, h2, h3, h4, h5, h6) .header-anchor:focus::after {
  opacity: 1;
}

pre,
code {
  font-family: 'SF Mono', Monaco, Menlo, 'Courier New', monospace;
  font-size: 14px;
  line-height: 24px;
}

:not(pre) > code {
  background: var(--color-code-background);
  padding: 0.1rem 0.35rem;
  border-radius: 3px;
  font-size: 0.9em;
}

pre {
  margin: 1.5rem 0;
  padding: 1rem;
  overflow-x: auto;
  background: var(--color-pre-background);
  border-radius: 6px;
}

/* Rouge's generated syntax.css sets its own `.highlight` background (to
   match its theme's own canvas color), which otherwise wins over the rule
   above since a class selector outranks a bare element selector. */
pre.highlight {
  background: var(--color-pre-background);
}

/* Rouge's generated github.dark theme sets a somewhat dim default token
   color (#c9d1d9) for unhighlighted code text; lighten it to match the
   rest of the page's body text. */
@media (prefers-color-scheme: dark) {
  pre.highlight,
  pre.highlight .w {
    color: var(--color-text);
  }
}

/* Tables scroll horizontally within this wrapper (added by default.html)
   instead of forcing the whole page wider than the viewport. */
.table-scroll {
  overflow-x: auto;
  margin: 1.5rem 0;
  -webkit-overflow-scrolling: touch;
}

table {
  border-collapse: collapse;
  width: 100%;
  margin: 1.5rem 0;
}

/* Inside the scroll wrapper the table grows with its content (and scrolls),
   but still fills the width when the content is narrow. */
.table-scroll table {
  width: max-content;
  min-width: 100%;
  margin: 0;
}

th,
td {
  border: 1px solid var(--color-subtle-border);
  padding: 0.5rem 0.75rem;
  text-align: left;
}

th {
  background: var(--color-code-background);
}

/* Footer */
.site-footer {
  margin-top: 3rem;
  color: #86868b;
  font-size: 14px;
  text-align: center;
}

.site-footer .nav-separator {
  margin: 0 0.5rem;
}

/* Responsive */
@media (max-width: 700px) {
  .nav-content {
    padding: 0.6rem 1rem;
    gap: 0.75rem;
    align-items: flex-start;
  }

  /* Stack the Contents button beneath the logo on the left. */
  .nav-left {
    flex-direction: column;
    align-items: flex-start;
    gap: 0.6rem;
  }

  .nav-links {
    gap: 0.9rem;
    flex-wrap: wrap;
    justify-content: flex-end;
  }

  .nav-separator {
    display: none;
  }

  .nav-link {
    font-size: 14px;
  }

  .nav-title {
    font-size: 16px;
  }

  /* The Contents button replaces the sidebar on mobile. */
  .toc-toggle {
    display: inline-block;
  }

  /* Single column; the TOC becomes a toggled full-screen overlay. */
  .page {
    grid-template-columns: minmax(0, 1fr);
    gap: 0;
    padding: 1.5rem;
  }

  /* Lock background scrolling while the TOC overlay is open. */
  body.toc-open {
    overflow: hidden;
  }

  .toc-sidebar {
    display: none;
    position: fixed;
    /* Reset the desktop rule's align-self: start, which otherwise breaks
       the top/bottom-based height resolution below and makes the overlay
       grow to its full content height instead of clipping to the viewport. */
    align-self: auto;
    top: var(--nav-height);
    left: 0;
    right: 0;
    bottom: 0;
    z-index: 90;
    min-height: 0;
    max-height: none;
    overflow-y: auto;
    background: var(--color-background);
    border-right: none;
    /* Unlike the desktop sidebar, show the scroll indicator here since this
       overlay covers the whole screen with no other affordance that it
       scrolls. */
    scrollbar-width: thin;
    -ms-overflow-style: auto;
  }

  .toc-sidebar::-webkit-scrollbar {
    display: block;
    width: 6px;
  }

  body.toc-open .toc-sidebar {
    display: block;
  }

  /* Roomier list with larger tap targets in the full-screen overlay. */
  .toc-sidebar #markdown-toc {
    padding: 1.25rem 1.5rem 2rem;
    font-size: 16px;
  }

  .toc-sidebar #markdown-toc a {
    padding: 0.3rem 0;
  }

  h1 {
    font-size: 32px;
    line-height: 36px;
  }

  h2 {
    font-size: 22px;
    line-height: 26px;
  }
}