/*
 * MarkDown One — the public pages.
 *
 * One stylesheet, no framework, no font file, no script. Everything here is
 * served from the same origin as the page, which is what lets these pages
 * make the same promise the application makes: opening one contacts nobody
 * but the host it was asked for. A web font or an analytics tag would be a
 * third-party request on a privacy policy, which is a contradiction.
 */

:root {
  color-scheme: light dark;

  /* The application's own palette, and not an approximation of it: `--accent`
     is `AppTheme._lightSeed`, `--accent-dark` is `_darkSeed`, and `--ink` is
     the near-black the launcher icon sits on. The bronze this file used
     before belongs to the Belksiri wordmark — the author's mark, not the
     product's — and it matched neither the icon nor a single pixel of the
     interface a visitor is about to download. */
  --ink: #12151b;
  --paper: #ffffff;
  --surface: #f7f8fa;
  --muted: #5a6270;
  --rule: #e4e7ec;
  --accent: #2563eb;
  --accent-ink: #1d4ed8;
  --on-accent: #ffffff;

  /* The shell and the reading measure are two different widths on purpose: a
     grid of cards wants room, a paragraph of policy wants about 70
     characters. */
  --page: 64rem;
  --measure: 38rem;

  --radius: 12px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --ink: #e8eaee;
    --paper: #0f1115;
    --surface: #171a20;
    --muted: #99a1af;
    --rule: #262a32;
    --accent: #4c8dff;
    --accent-ink: #8ab4ff;
    --on-accent: #0f1115;
  }
}

* { box-sizing: border-box; }

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

/* An in-page jump is the only motion on this site, and some readers get
   motion sick from it. */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  * { transition: none !important; }
}

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
    "Helvetica Neue", Arial, "Noto Sans", sans-serif;
  font-size: 17px;
  line-height: 1.65;
  text-rendering: optimizeLegibility;
}

/* The centred gutter. Everything on every page sits in one of these. */
.wrap {
  max-width: var(--page);
  margin: 0 auto;
  padding: 0 1.5rem;
}

/* The two reading pages are `<main class="wrap">`, and a policy read at
   64rem is a policy nobody finishes. The landing page opts out by not being
   a `.wrap` itself: its sections carry their own. */
main.wrap { max-width: var(--measure); }

/* A block of prose inside a wide section. */
.prose { max-width: var(--measure); }

/* Reachable by keyboard, invisible until it is focused — which is the point:
   the first Tab on any page skips the navigation. */
.skip {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--accent);
  color: var(--on-accent);
  padding: 0.6rem 1rem;
  border-radius: 0 0 var(--radius) 0;
  z-index: 10;
}

.skip:focus {
  left: 0;
}

/* ---------------------------------------------------------------- header */

header {
  position: sticky;
  top: 0;
  z-index: 5;
  background: color-mix(in srgb, var(--paper) 88%, transparent);
  backdrop-filter: saturate(180%) blur(12px);
  -webkit-backdrop-filter: saturate(180%) blur(12px);
  border-bottom: 1px solid var(--rule);
}

header .wrap {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem 1.5rem;
  padding-top: 0.85rem;
  padding-bottom: 0.85rem;
}

header nav ul {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem 1.4rem;
  margin: 0;
  padding: 0;
}

header nav a {
  color: var(--muted);
  text-decoration: none;
  /* 44 px of height on a phone, which is the smallest target a thumb hits
     reliably. */
  display: inline-block;
  padding: 0.5rem 0;
  font-size: 0.95rem;
}

header nav a:hover { color: var(--ink); }

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.55rem;
  font-size: 1.1rem;
  font-weight: 600;
  letter-spacing: -0.015em;
  text-decoration: none;
  color: inherit;
}

.brand img {
  width: 26px;
  height: 26px;
  border-radius: 6px;
}

.brand .accent { color: var(--accent-ink); }

/* ------------------------------------------------------------------ main */

main { display: block; }

section { scroll-margin-top: 5rem; }

h1 {
  font-size: clamp(2.1rem, 5vw, 3rem);
  line-height: 1.1;
  letter-spacing: -0.03em;
  margin: 0 0 0.75rem;
}

h2 {
  font-size: 1.45rem;
  line-height: 1.25;
  letter-spacing: -0.02em;
  margin: 0 0 0.5rem;
}

h3 {
  font-size: 1rem;
  line-height: 1.35;
  margin: 0 0 0.3rem;
}

p, ul, ol, table { margin: 0 0 1rem; }

.lead {
  font-size: 1.15rem;
  color: var(--muted);
  margin-bottom: 2rem;
}

.tagline {
  font-size: 1.05rem;
  color: var(--accent-ink);
  font-weight: 600;
  letter-spacing: 0.01em;
  margin: 0 0 1rem;
}

/* The small label above a section heading. */
.eyebrow {
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.09em;
  text-transform: uppercase;
  color: var(--muted);
  margin: 0 0 0.5rem;
}

ul, ol { padding-left: 1.35rem; }
li { margin-bottom: 0.35rem; }

a { color: var(--accent-ink); }
a:hover { text-decoration: none; }

/* A visible ring, not the browser's default outline removed and forgotten. */
a:focus-visible,
.button:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
  border-radius: 4px;
}

/* ---------------------------------------------------------------- pieces */

.hero {
  padding: 4.5rem 0 3.5rem;
  border-bottom: 1px solid var(--rule);
}

.hero .mark {
  width: 88px;
  height: 88px;
  border-radius: 20px;
  margin-bottom: 1.5rem;
  display: block;
}

.hero .lead { max-width: var(--measure); }

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin: 0;
}

.button {
  display: inline-block;
  padding: 0.7rem 1.3rem;
  border: 1px solid var(--rule);
  border-radius: 8px;
  text-decoration: none;
  color: inherit;
  font-weight: 500;
  transition: border-color 0.15s ease, background-color 0.15s ease;
}

.button:hover { border-color: var(--accent); }

.button.primary {
  background: var(--accent);
  border-color: var(--accent);
  color: var(--on-accent);
}

.button.primary:hover {
  background: var(--accent-ink);
  border-color: var(--accent-ink);
}

section.pad { padding: 3.5rem 0; }

.band {
  background: var(--surface);
  border-top: 1px solid var(--rule);
  border-bottom: 1px solid var(--rule);
}

/* Cards, and the one grid rule the whole page uses. `auto-fit` with a
   minimum is what makes 320 px, 768 px and 1440 px the same stylesheet
   rather than three breakpoints. */
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(15.5rem, 1fr));
  gap: 1rem;
  margin: 2rem 0 0;
  padding: 0;
  list-style: none;
}

.grid.narrow {
  grid-template-columns: repeat(auto-fit, minmax(11rem, 1fr));
}

.card {
  background: var(--surface);
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  padding: 1.35rem;
  margin: 0;
}

.card p {
  margin: 0;
  color: var(--muted);
  font-size: 0.95rem;
}

/* The availability of one platform, stated rather than implied. */
.pill {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  padding: 0.15rem 0.55rem;
  border-radius: 999px;
  border: 1px solid var(--rule);
  color: var(--muted);
  background: var(--paper);
  margin-top: 0.6rem;
}

/* -------------------------------------------- the two long reading pages */

main.wrap { padding-top: 2.5rem; padding-bottom: 3rem; }

main.wrap h2 {
  font-size: 1.25rem;
  margin: 2.5rem 0 0.5rem;
  padding-top: 0.5rem;
  border-top: 1px solid var(--rule);
}

main.wrap h3 {
  margin: 1.75rem 0 0.35rem;
}

code {
  font-family: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas,
    monospace;
  font-size: 0.9em;
  background: color-mix(in srgb, var(--rule) 45%, transparent);
  padding: 0.1em 0.35em;
  border-radius: 3px;
}

.note {
  border-left: 3px solid var(--accent);
  padding: 0.1rem 0 0.1rem 1rem;
  margin: 1.5rem 0;
  color: var(--muted);
}

.flow {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.85rem;
  overflow-x: auto;
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  padding: 0.9rem 1rem;
  margin: 1.25rem 0;
}

/* A wide table on a narrow phone scrolls inside itself; the page never does. */
.scroll { overflow-x: auto; margin: 0 0 1.25rem; }

table {
  border-collapse: collapse;
  width: 100%;
  font-size: 0.95rem;
}

th, td {
  text-align: left;
  vertical-align: top;
  padding: 0.5rem 0.75rem 0.5rem 0;
  border-bottom: 1px solid var(--rule);
}

th { font-weight: 600; }

.meta {
  color: var(--muted);
  font-size: 0.95rem;
  margin-bottom: 2rem;
}

.meta div { margin-bottom: 0.15rem; }

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

footer {
  border-top: 1px solid var(--rule);
  padding: 2.5rem 0;
  color: var(--muted);
  font-size: 0.9rem;
}

footer .brand {
  font-size: 1rem;
  margin-bottom: 0.9rem;
}

footer nav ul {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem 1.5rem;
  margin: 0 0 0.75rem;
  padding: 0;
}

footer p { margin: 0; }

@media (max-width: 30rem) {
  body { font-size: 16px; }
  .wrap { padding: 0 1.15rem; }
  /* Four navigation items on one line at 320 px, spread rather than wrapped:
     the widths are known and they fit, but only if the gap gives way first. */
  header nav { width: 100%; }
  header nav ul { justify-content: space-between; gap: 0.25rem 0.7rem; }
  .hero { padding: 3rem 0 2.5rem; }
  .hero .mark { width: 72px; height: 72px; border-radius: 16px; }
  section.pad { padding: 2.75rem 0; }
  .actions .button { flex: 1 1 100%; text-align: center; }
}