/* rail0 — protocol site
   Minimal / RFC aesthetic: monochrome ink, one restrained accent,
   monospace accents, whitespace-heavy. Light + dark via prefers-color-scheme.
   No build step, no dependencies. */

:root {
  --ink: #1c1814;
  --ink-soft: #4a443c;
  --ink-faint: #8a8175;
  --line: #ece7dc;
  --line-soft: #f4efe6;
  --bg: #faf7f0;
  --bg-soft: #f4efe5;
  --bg-code: #f1ebe0;
  --card: #ffffff;
  --accent: #2f7d72;
  --accent-soft: rgba(47, 125, 114, 0.13);
  --mono: ui-monospace, "SF Mono", "JetBrains Mono", "Fira Code", Menlo, Consolas, monospace;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Inter, Roboto, Helvetica, Arial, sans-serif;
  --serif: "Lora", Georgia, "Times New Roman", serif;
  --maxw: 880px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --ink: #fafafa;
    --ink-soft: #d4d4d8;
    --ink-faint: #a1a1aa;
    --line: #27272a;
    --line-soft: #1c1c1f;
    --bg: #0a0a0b;
    --bg-soft: #111113;
    --bg-code: #141417;
    --card: #151518;
    --accent: #5cc0b2;
    --accent-soft: rgba(92, 192, 178, 0.14);
  }
}

* { box-sizing: border-box; }

/* Smooth scrolling for in-page anchor clicks only. Gating on :focus-within
   keeps it from animating the browser's scroll restoration on refresh
   (which otherwise reads as the page drifting "up" a little on reload). */
@media (prefers-reduced-motion: no-preference) {
  html:focus-within { scroll-behavior: smooth; }
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 17px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

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

.wrap {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 0 24px;
}

/* ---- generic section rhythm ---- */
section { padding: 72px 0; border-top: 1px solid var(--line-soft); }
section:first-of-type { border-top: none; }

.eyebrow {
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-faint);
  margin: 0 0 18px;
}

h2 {
  font-family: var(--serif);
  font-size: 32px;
  line-height: 1.18;
  font-weight: 600;
  letter-spacing: -0.015em;
  margin: 0 0 20px;
}

h3 { font-size: 17px; font-weight: 650; margin: 0 0 8px; letter-spacing: -0.01em; }

p { margin: 0 0 18px; color: var(--ink-soft); }
p:last-child { margin-bottom: 0; }
strong { color: var(--ink); font-weight: 600; }

code {
  font-family: var(--mono);
  font-size: 0.88em;
  background: var(--bg-code);
  border: 1px solid var(--line);
  border-radius: 5px;
  padding: 1px 5px;
}

/* ---- top nav ---- */
header.nav {
  position: sticky;
  top: 0;
  z-index: 10;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: saturate(140%) blur(10px);
  border-bottom: 1px solid var(--line-soft);
}
header.nav .wrap {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 60px;
}
.brandmark { display: flex; align-items: center; gap: 9px; }
.brandmark img { height: 24px; width: auto; display: block; }
.brandmark .v {
  font-family: var(--mono);
  font-size: 11px;
  color: var(--ink-faint);
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 1px 7px;
}
.nav-links { display: flex; align-items: center; gap: 26px; }
.nav-links a {
  color: var(--ink-soft);
  font-size: 16px;
  font-weight: 500;
}
.nav-links a:hover { color: var(--ink); text-decoration: none; }
@media (max-width: 620px) { .nav-links a.hide-sm { display: none; } }

/* ---- hero ---- */
.hero { padding: 96px 0 80px; text-align: left; }
.hero .logo-payoff { width: 320px; max-width: 78%; height: auto; margin-bottom: 36px; }
.hero h1 {
  font-family: var(--serif);
  font-size: 72px;
  line-height: 1.06;
  font-weight: 600;
  letter-spacing: -0.022em;
  margin: 0 0 24px;
  max-width: 15ch;
}
@media (max-width: 900px) { .hero h1 { font-size: 58px; } }
@media (max-width: 620px) { .hero h1 { font-size: 42px; } }

/* ---- manifesto (long-form prose) ---- */
.manifesto { max-width: 64ch; margin-top: 8px; }
.manifesto p {
  font-size: 19px;
  line-height: 1.7;
  margin-bottom: 22px;
  color: var(--ink-soft);
}
.manifesto p.lead { color: var(--ink); }
.manifesto .cta-row { margin-top: 38px; }

/* payer -> escrow -> payee protocol diagram
   Wide desktop artwork above the breakpoint, tall mobile redraw below. */
.protocol-diagram { margin-top: 56px; }
.protocol-diagram img {
  display: block;
  width: 100%;
  height: auto;
  margin: 0 auto;
}
.protocol-diagram .dia-mobile { display: none; }
@media (max-width: 640px) {
  .protocol-diagram .dia-desktop { display: none; }
  .protocol-diagram .dia-mobile { display: block; max-width: 420px; }
}
.hero .lede { font-size: 19px; max-width: 60ch; margin-bottom: 34px; }

.cta-row { display: flex; flex-wrap: wrap; gap: 12px; }
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 15px;
  font-weight: 550;
  padding: 11px 20px;
  border-radius: 9px;
  border: 1px solid var(--ink);
  transition: opacity 0.15s ease, transform 0.05s ease;
}
.btn:hover { text-decoration: none; opacity: 0.86; }
.btn:active { transform: translateY(1px); }
.btn-primary { background: var(--ink); color: var(--bg); }
.btn-ghost { background: transparent; color: var(--ink); border-color: var(--line); }
.btn svg { width: 16px; height: 16px; }

/* ---- the four zeros ---- */
.zeros {
  margin-top: 56px;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
  border-radius: 12px;
  overflow: hidden;
}
.zero { background: var(--card); padding: 26px 22px; }
.zero .num {
  font-family: var(--mono);
  font-size: 34px;
  font-weight: 600;
  letter-spacing: -0.04em;
  color: var(--accent);
  line-height: 1;
  margin-bottom: 14px;
}
.zero h3 { margin-bottom: 4px; }
.zero p { font-size: 14px; line-height: 1.5; }
@media (max-width: 720px) { .zeros { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 420px) { .zeros { grid-template-columns: 1fr; } }

/* ---- lifecycle diagram ---- */
.flow {
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--bg-soft);
  padding: 30px 26px;
}
.flow-track {
  display: flex;
  align-items: stretch;
  gap: 0;
  flex-wrap: wrap;
}
.node {
  flex: 1 1 0;
  min-width: 150px;
  background: var(--bg);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 16px 18px;
}
.node .op {
  font-family: var(--mono);
  font-size: 15px;
  font-weight: 600;
  color: var(--ink);
}
.node .who {
  font-family: var(--mono);
  font-size: 11px;
  color: var(--ink-faint);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-top: 2px;
}
.node p { font-size: 13.5px; line-height: 1.5; margin: 9px 0 0; }
.arrow {
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--ink-faint);
  font-family: var(--mono);
  padding: 0 4px;
  flex: 0 0 auto;
}
@media (max-width: 680px) {
  .flow-track { flex-direction: column; }
  .arrow { transform: rotate(90deg); padding: 6px 0; }
}
.branches {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 14px;
  margin-top: 22px;
}
.branch {
  border-top: 2px solid var(--line);
  padding-top: 12px;
}
.branch .op {
  font-family: var(--mono);
  font-size: 13.5px;
  font-weight: 600;
}
.branch p { font-size: 12.5px; line-height: 1.45; margin: 4px 0 0; color: var(--ink-faint); }
@media (max-width: 720px) { .branches { grid-template-columns: repeat(2, 1fr); } }

/* ---- how it works: steps ---- */
.steps { display: grid; grid-template-columns: repeat(3, 1fr); gap: 22px; }
.step .k {
  font-family: var(--mono);
  font-size: 12px;
  color: var(--accent);
  margin-bottom: 10px;
}
.step h3 { margin-bottom: 6px; }
.step p { font-size: 14.5px; line-height: 1.55; }
@media (max-width: 720px) { .steps { grid-template-columns: 1fr; gap: 28px; } }

/* ---- chains table ---- */
.table-scroll { margin-top: 56px; overflow-x: auto; border: 1px solid var(--line); border-radius: 12px; background: var(--card); }
table { border-collapse: collapse; width: 100%; font-size: 14.5px; }
thead th {
  text-align: left;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink-faint);
  font-weight: 600;
  padding: 14px 18px;
  background: var(--card);
  border-bottom: 1px solid var(--line);
}
tbody td { padding: 14px 18px; border-bottom: 1px solid var(--line-soft); color: var(--ink-soft); }
tbody tr:last-child td { border-bottom: none; }
tbody td:first-child { color: var(--ink); font-weight: 550; }
td code { font-size: 12.5px; }
.tag {
  font-family: var(--mono);
  font-size: 11px;
  padding: 2px 8px;
  border-radius: 999px;
  border: 1px solid var(--line);
  color: var(--ink-faint);
}
.tag.live { color: #0f8a3d; border-color: rgba(15, 138, 61, 0.35); }
@media (prefers-color-scheme: dark) { .tag.live { color: #4ade80; border-color: rgba(74, 222, 128, 0.3); } }

/* ---- quickstart steps ---- */
.qs-step { margin-top: 44px; }
.qs-step:first-of-type { margin-top: 36px; }
.qs-step h3 { margin-bottom: 6px; }
.qs-step > p { font-size: 14.5px; margin-bottom: 16px; }

/* ---- quickstart CTA ---- */
.qs-cta {
  margin-top: 48px;
  padding-top: 36px;
  border-top: 1px solid var(--line);
  display: flex;
  flex-direction: column-reverse;  /* mobile: text on top, button below */
  align-items: flex-start;
  text-align: left;
  gap: 18px;
}
.qs-cta .btn { flex: 0 0 auto; }
.qs-cta p {
  margin: 0;
  font-size: 17px;
  color: var(--ink);
  max-width: 42ch;
}
@media (min-width: 640px) {
  .qs-cta {
    flex-direction: row;           /* desktop: button left, text right */
    align-items: center;
    gap: 24px;
  }
}

/* ---- code block (warm-dark terminal, fixed across themes) ---- */
.code-block {
  background: #1c1a17;
  border: 1px solid #2c2925;
  border-radius: 12px;
  overflow: hidden;
}
.code-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 16px;
  border-bottom: 1px solid #2c2925;
  font-family: var(--mono);
  font-size: 12px;
  color: #8c8579;
}
.code-block pre {
  margin: 0;
  padding: 18px 20px;
  overflow-x: auto;
  font-family: var(--mono);
  font-size: 13px;
  line-height: 1.7;
  color: #ece7dc;
}
.code-block .c { color: #8c8579; }   /* comment  */
.code-block .k { color: #5cc0b2; }   /* keyword/cmd — teal accent */
.code-block .s { color: #e0a54a; }   /* string-ish — amber */

.note {
  font-size: 14px;
  color: var(--ink-faint);
  margin-top: 18px;
}

/* ---- footer ---- */
footer {
  border-top: 1px solid var(--line);
  padding: 48px 0 64px;
}
footer .grid {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 24px;
  flex-wrap: wrap;
}
footer img.fmark { height: 16px; width: auto; opacity: 0.8; }
footer .meta { font-family: var(--mono); font-size: 12.5px; color: var(--ink-faint); line-height: 1.9; }
footer .links { display: flex; gap: 22px; font-size: 14px; }
footer .links a { color: var(--ink-soft); }
footer .disclaimer {
  margin-top: 28px;
  font-size: 12.5px;
  color: var(--ink-faint);
  border-top: 1px solid var(--line-soft);
  padding-top: 20px;
}

/* light/dark logo swap — !important so the toggle beats the more specific
   `.brandmark img` / `footer img.fmark` display rules */
.only-dark { display: none !important; }
@media (prefers-color-scheme: dark) {
  .only-light { display: none !important; }
  .only-dark { display: block !important; }
}