:root {
  --bg: #ffffff;
  --bg-soft: #f3f8f6;
  --card: #ffffff;
  --text: #10201b;
  --muted: #55665f;
  --line: #dce7e3;
  --brand: #0a9f80;
  --brand-strong: #00734d;
  --brand-soft: #e2f6f0;
  --on-brand: #ffffff;
  --mark: #fff1c2;
  --radius: 16px;
  --font: -apple-system, BlinkMacSystemFont, "SF Pro Text", "PingFang SC", "PingFang TC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans CJK SC", "Segoe UI", Roboto, sans-serif;
  --mono: ui-monospace, "SF Mono", Menlo, Consolas, monospace;
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0b1210;
    --bg-soft: #111c19;
    --card: #14211d;
    --text: #e6f0ec;
    --muted: #9db0a9;
    --line: #22332e;
    --brand: #2fd3ad;
    --brand-strong: #5ee6c4;
    --brand-soft: #123a30;
    --on-brand: #04241b;
    --mark: #4a3d10;
    color-scheme: dark;
  }
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 17px/1.7 var(--font);
  -webkit-font-smoothing: antialiased;
}
a { color: var(--brand-strong); text-decoration-thickness: 1px; text-underline-offset: 3px; }
img { max-width: 100%; }
code { font-family: var(--mono); font-size: .9em; background: var(--bg-soft); border: 1px solid var(--line); border-radius: 6px; padding: 0 .3em; }
pre { font-family: var(--mono); font-size: 14px; line-height: 1.6; background: var(--bg-soft); border: 1px solid var(--line); border-radius: 12px; padding: 14px 16px; overflow-x: auto; }
pre code { background: none; border: 0; padding: 0; }

.wrap { max-width: 1080px; margin: 0 auto; padding: 0 20px; }

/* header */
.site-header {
  position: sticky; top: 0; z-index: 10;
  background: color-mix(in srgb, var(--bg) 86%, transparent);
  backdrop-filter: saturate(1.6) blur(14px);
  -webkit-backdrop-filter: saturate(1.6) blur(14px);
  border-bottom: 1px solid var(--line);
}
.bar { display: flex; align-items: center; gap: 24px; min-height: 60px; flex-wrap: wrap; }
.brand { display: flex; align-items: center; gap: 10px; color: var(--text); text-decoration: none; font-weight: 700; font-size: 19px; letter-spacing: -.01em; }
.brand img { border-radius: 8px; }
.nav, .lang { display: flex; gap: 18px; font-size: 15px; }
.nav { flex: 1; }
.nav a, .lang a { color: var(--muted); text-decoration: none; white-space: nowrap; }
.nav a:hover, .lang a:hover { color: var(--text); }
.nav a[aria-current], .lang a[aria-current] { color: var(--text); font-weight: 600; }
.lang { gap: 12px; font-size: 14px; }

/* hero */
.hero { padding: 72px 0 56px; background: radial-gradient(1200px 500px at 70% -10%, var(--brand-soft), transparent 70%); }
.hero-grid { display: grid; grid-template-columns: 1.1fr .9fr; gap: 48px; align-items: center; }
.eyebrow { display: inline-block; font-size: 14px; font-weight: 600; color: var(--brand-strong); background: var(--brand-soft); border-radius: 999px; padding: 3px 12px; margin: 0 0 18px; }
.nw { white-space: nowrap; }
h1 { font-size: clamp(30px, 4.6vw, 52px); line-height: 1.15; letter-spacing: -.02em; margin: 0 0 20px; }
.lead { font-size: 19px; color: var(--muted); margin: 0 0 28px; max-width: 34em; }
.actions { display: flex; flex-wrap: wrap; gap: 12px; align-items: center; }
.btn { display: inline-flex; align-items: center; gap: 8px; padding: 11px 20px; border-radius: 999px; font-weight: 600; font-size: 16px; text-decoration: none; border: 1px solid var(--line); color: var(--text); background: var(--card); }
.btn.primary { background: var(--brand); border-color: var(--brand); color: var(--on-brand); }
.btn:hover { filter: brightness(1.05); }
.note { font-size: 14px; color: var(--muted); margin-top: 14px; }

/* the flow picture */
.flow { width: 100%; height: auto; }
.flow .box { fill: var(--card); stroke: var(--line); stroke-width: 2; }
.flow .phone { fill: var(--bg-soft); stroke: var(--text); stroke-width: 3; }
.flow .screen { fill: var(--brand-soft); }
.flow .label { fill: var(--text); font: 600 15px var(--font); }
.flow .small { fill: var(--muted); font: 13px var(--font); }
.flow .link { stroke: var(--brand); stroke-width: 3; fill: none; stroke-dasharray: 2 7; stroke-linecap: round; }
.flow .lock { fill: var(--brand); }
.flow .lock-text { fill: var(--on-brand); font: 700 12px var(--font); }
.flow .sim { fill: var(--brand); }

/* sections */
section { padding: 72px 0; }
section.soft { background: var(--bg-soft); border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); }
h2 { font-size: clamp(26px, 3.4vw, 36px); line-height: 1.25; letter-spacing: -.01em; margin: 0 0 12px; }
.section-lead { color: var(--muted); font-size: 18px; margin: 0 0 36px; max-width: 40em; }
h3 { font-size: 19px; margin: 0 0 8px; line-height: 1.4; }

.grid { display: grid; gap: 18px; grid-template-columns: repeat(3, 1fr); }
.grid.two { grid-template-columns: repeat(2, 1fr); }
.card { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 22px 22px 18px; }
.card p, .card ul { margin: 0; color: var(--muted); font-size: 16px; }
.card ul { padding-left: 1.1em; }
.card li + li { margin-top: 4px; }
.card .tag { display: inline-block; font-size: 12px; font-weight: 600; color: var(--brand-strong); background: var(--brand-soft); border-radius: 999px; padding: 1px 9px; margin-left: 6px; vertical-align: 2px; }
.icon { width: 40px; height: 40px; border-radius: 11px; background: var(--brand-soft); color: var(--brand-strong); display: grid; place-items: center; margin-bottom: 14px; }
.icon svg { width: 22px; height: 22px; fill: none; stroke: currentColor; stroke-width: 2; stroke-linecap: round; stroke-linejoin: round; }

.steps { counter-reset: step; display: grid; gap: 18px; grid-template-columns: repeat(3, 1fr); padding: 0; margin: 0; list-style: none; }
.steps li { counter-increment: step; background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 22px; color: var(--muted); font-size: 16px; }
.steps li::before { content: counter(step); display: grid; place-items: center; width: 32px; height: 32px; border-radius: 50%; background: var(--brand); color: var(--on-brand); font-weight: 700; margin-bottom: 12px; }
.steps strong { display: block; color: var(--text); font-size: 18px; margin-bottom: 4px; }

.parts { width: 100%; border-collapse: collapse; font-size: 16px; }
.table { overflow-x: auto; }
table { width: 100%; border-collapse: collapse; font-size: 15px; }
th, td { text-align: left; vertical-align: top; padding: 12px 14px; border-bottom: 1px solid var(--line); }
th { font-weight: 600; color: var(--muted); font-size: 14px; }
.open { color: var(--brand-strong); font-weight: 600; white-space: nowrap; }
.closed { color: var(--muted); white-space: nowrap; }

.status { list-style: none; padding: 0; margin: 0; display: grid; gap: 10px; }
.status li { background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 12px 16px; font-size: 16px; }
.status b { color: var(--text); }

details { border-bottom: 1px solid var(--line); padding: 16px 0; }
details summary { cursor: pointer; font-weight: 600; font-size: 18px; list-style: none; position: relative; padding-right: 28px; }
details summary::-webkit-details-marker { display: none; }
details summary::after { content: "+"; position: absolute; right: 4px; top: -2px; font-size: 22px; color: var(--muted); }
details[open] summary::after { content: "–"; }
details p { color: var(--muted); margin: 10px 0 0; }

.callout { border-left: 4px solid var(--brand); background: var(--brand-soft); border-radius: 0 12px 12px 0; padding: 14px 18px; margin: 24px 0; font-size: 16px; }
.callout p { margin: 0; }

/* simple content pages (gateway, relay) */
.page-head { padding: 56px 0 8px; }
.page-head .lead { margin-bottom: 0; }
.prose { max-width: 760px; }
.prose h2 { margin-top: 48px; font-size: 26px; }
.prose p, .prose li { color: var(--text); }
.prose ul, .prose ol { padding-left: 1.3em; }

/* legal */
.legal { max-width: 800px; padding-top: 40px; padding-bottom: 72px; }
.legal h1 { font-size: 36px; }
.legal h2 { font-size: 24px; margin-top: 40px; }
.legal h3 { font-size: 19px; margin-top: 28px; }
.legal p, .legal li { font-size: 16px; }
mark.todo { background: var(--mark); color: inherit; border-radius: 4px; padding: 0 2px; }
.draft-note { margin-top: 24px; color: var(--muted); font-size: 14px; }

/* footer */
.site-footer { border-top: 1px solid var(--line); padding: 32px 0 48px; color: var(--muted); font-size: 14px; }
.site-footer p { margin: 6px 0; }
.site-footer a { color: var(--muted); }
.foot-brand { display: flex; align-items: center; gap: 8px; color: var(--text); font-weight: 600; }
.foot-brand img { border-radius: 6px; }

@media (max-width: 860px) {
  .hero { padding: 40px 0 32px; }
  .hero-grid, .grid, .grid.two, .steps { grid-template-columns: 1fr; }
  .hero-grid { gap: 28px; }
  section { padding: 52px 0; }
  .wrap { padding: 0 16px; }
  .bar { gap: 6px 18px; padding-top: 10px; padding-bottom: 10px; }
  .parts th:nth-child(2), .parts td:nth-child(2) { display: none; }
  .parts .open, .parts .closed { white-space: normal; }
  th, td { padding: 10px 8px; }
  .nav { order: 3; flex-basis: 100%; gap: 14px; overflow-x: auto; scrollbar-width: none; }
  .lang { margin-left: auto; }
}

/* iPhone app page: screenshots */
.shots { display: flex; gap: 18px; justify-content: center; align-items: flex-start; }
.shot { margin: 0; flex: 0 1 260px; min-width: 0; }
.shot img { display: block; width: 100%; height: auto; border-radius: 34px; border: 1px solid var(--line); box-shadow: 0 18px 50px -20px rgba(0, 60, 40, .35); background: var(--card); }
.shot figcaption { text-align: center; font-size: 14px; color: var(--muted); margin-top: 10px; }
.hero .shots .shot:nth-child(2) { margin-top: 48px; }
.feature { display: grid; grid-template-columns: 1fr 1.1fr; gap: 56px; align-items: center; }
.feature.flip > :first-child { order: 2; }
.feature ul { padding-left: 1.2em; color: var(--muted); margin: 16px 0 0; }
.feature li + li { margin-top: 6px; }
.feature p { color: var(--muted); }
.mini { display: grid; grid-template-columns: repeat(4, 1fr); gap: 18px; }
@media (max-width: 860px) {
  .feature { grid-template-columns: 1fr; gap: 28px; }
  .feature.flip > :first-child { order: 0; }
  .mini { grid-template-columns: 1fr 1fr; }
  .shots { gap: 12px; }
  .shot img { border-radius: 24px; }
  .hero .shots .shot:nth-child(2) { margin-top: 28px; }
}