/* ============================================================
   5C Exchange — marketing site
   Design system: warm paper · ink · one muted evergreen accent
   ============================================================ */

:root {
  /* Color */
  --paper:     #F7F5F0;
  --paper-2:   #F1EFE8;   /* alternating section band */
  --ink:       #1B1D1A;
  --evergreen: #2F4A3C;
  --evergreen-deep: #233A2E;
  --sage:      #E6E9E2;
  --stone:     #6E726A;   /* secondary text */
  --line:      #D9D7CE;   /* hairlines */
  --line-soft: #E7E4DB;

  /* Type */
  --serif: "Source Serif 4", Georgia, "Times New Roman", serif;
  --sans:  "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --mono:  "IBM Plex Mono", ui-monospace, "SF Mono", Menlo, monospace;

  /* Scale */
  --maxw: 1080px;
  --gut: clamp(20px, 5vw, 48px);
  --radius: 4px;

  --step--1: clamp(0.82rem, 0.8rem + 0.1vw, 0.88rem);
  --step-0:  clamp(1rem, 0.97rem + 0.15vw, 1.075rem);
  --step-1:  clamp(1.2rem, 1.12rem + 0.4vw, 1.4rem);
  --step-2:  clamp(1.5rem, 1.35rem + 0.75vw, 1.95rem);
  --step-3:  clamp(2rem, 1.7rem + 1.5vw, 3rem);
  --step-4:  clamp(2.6rem, 2.05rem + 2.75vw, 4.25rem);
}

/* ---------- Reset ---------- */
*, *::before, *::after { box-sizing: border-box; }
* { margin: 0; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation-duration: 0.001ms !important; transition-duration: 0.001ms !important; }
}

body {
  font-family: var(--sans);
  font-size: var(--step-0);
  line-height: 1.6;
  color: var(--ink);
  background: var(--paper);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

img { max-width: 100%; display: block; }
a { color: inherit; }

h1, h2, h3, h4 { font-family: var(--serif); font-weight: 500; line-height: 1.12; letter-spacing: -0.01em; }
p { text-wrap: pretty; }

.container { width: 100%; max-width: var(--maxw); margin-inline: auto; padding-inline: var(--gut); }

/* Eyebrow / ledger labels */
.eyebrow {
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--evergreen);
  display: inline-flex;
  align-items: center;
  gap: 0.55em;
}
.eyebrow::before {
  content: "";
  width: 20px; height: 1px;
  background: var(--evergreen);
  display: inline-block;
}

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex; align-items: center; gap: 0.5em;
  font-family: var(--sans); font-size: var(--step--1); font-weight: 500;
  letter-spacing: 0.01em;
  padding: 0.72em 1.25em;
  border-radius: var(--radius);
  border: 1px solid transparent;
  text-decoration: none; cursor: pointer;
  transition: background-color .18s ease, color .18s ease, border-color .18s ease, transform .18s ease;
}
.btn:active { transform: translateY(1px); }
.btn-primary { background: var(--evergreen); color: #fff; }
.btn-primary:hover { background: var(--evergreen-deep); }
.btn-ghost { background: transparent; color: var(--ink); border-color: var(--line); }
.btn-ghost:hover { border-color: var(--ink); }
.btn[aria-disabled="true"] { opacity: .45; pointer-events: none; }
.btn svg { width: 1.05em; height: 1.05em; }

/* ---------- Header ---------- */
.site-header {
  position: sticky; top: 0; z-index: 50;
  background: color-mix(in srgb, var(--paper) 88%, transparent);
  backdrop-filter: saturate(120%) blur(8px);
  border-bottom: 1px solid transparent;
  transition: border-color .2s ease, background-color .2s ease;
}
.site-header.scrolled { border-bottom-color: var(--line); }
.nav { display: flex; align-items: center; justify-content: space-between; height: 66px; }
.brand { display: inline-flex; align-items: center; gap: 0.6em; text-decoration: none; color: var(--ink); }
.brand .mark { width: 26px; height: 26px; }
.brand .name { font-family: var(--serif); font-size: 1.18rem; font-weight: 500; letter-spacing: -0.01em; }
.nav-links { display: flex; align-items: center; gap: clamp(14px, 2vw, 30px); list-style: none; }
.nav-links a { text-decoration: none; color: var(--stone); font-size: var(--step--1); font-weight: 500; transition: color .15s ease; }
.nav-links a:hover { color: var(--ink); }
.nav-cta { display: flex; align-items: center; gap: 12px; }
.hamburger { display: none; background: none; border: 0; padding: 8px; cursor: pointer; color: var(--ink); }

/* mobile nav */
.mobile-menu { display: none; }
@media (max-width: 760px) {
  .nav-links, .nav-cta .btn-ghost { display: none; }
  .hamburger { display: inline-flex; }
  .mobile-menu {
    display: block; position: fixed; inset: 66px 0 auto 0; z-index: 49;
    background: var(--paper); border-bottom: 1px solid var(--line);
    transform: translateY(-120%); transition: transform .28s ease; padding: 8px var(--gut) 24px;
  }
  .mobile-menu.open { transform: translateY(0); }
  .mobile-menu ul { list-style: none; padding: 0; }
  .mobile-menu li { border-bottom: 1px solid var(--line-soft); }
  .mobile-menu a { display: block; padding: 16px 2px; text-decoration: none; color: var(--ink); font-weight: 500; }
  .mobile-menu .btn { width: 100%; justify-content: center; margin-top: 18px; }
}

/* ---------- Sections ---------- */
section { padding-block: clamp(56px, 9vw, 104px); }
.band { background: var(--paper-2); }
.section-head { max-width: 60ch; margin-bottom: clamp(28px, 4vw, 44px); }
.section-head h2 { font-size: var(--step-3); margin-top: 14px; }
.section-head p { color: var(--stone); margin-top: 14px; font-size: var(--step-1); line-height: 1.5; }

/* ---------- Hero ---------- */
.hero { padding-top: clamp(48px, 7vw, 84px); padding-bottom: 0; }
.hero h1 { font-size: var(--step-4); max-width: 16ch; margin-top: 20px; }
.hero .lede { font-size: var(--step-1); color: var(--stone); max-width: 46ch; margin-top: 22px; line-height: 1.5; }
.hero-actions { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 30px; align-items: center; }
.hero-note { font-family: var(--mono); font-size: 0.74rem; color: var(--stone); margin-top: 18px; letter-spacing: 0.02em; }

/* ledger strip */
.ledger {
  margin-top: clamp(44px, 6vw, 72px);
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  display: grid; grid-template-columns: repeat(4, 1fr);
}
.ledger div { padding: 22px clamp(10px, 2vw, 26px); border-left: 1px solid var(--line); }
.ledger div:first-child { border-left: 0; }
.ledger .fig { font-family: var(--mono); font-size: var(--step-2); color: var(--ink); line-height: 1; }
.ledger .lab { font-family: var(--mono); font-size: 0.68rem; letter-spacing: 0.1em; text-transform: uppercase; color: var(--stone); margin-top: 10px; }
@media (max-width: 680px) {
  .ledger { grid-template-columns: 1fr 1fr; }
  .ledger div:nth-child(3) { border-left: 0; }
  .ledger div:nth-child(2), .ledger div:nth-child(4) { border-left: 1px solid var(--line); }
  .ledger div:nth-child(3), .ledger div:nth-child(4) { border-top: 1px solid var(--line); }
}

/* ---------- What it is ---------- */
.lead-statement p { font-size: var(--step-2); font-family: var(--serif); line-height: 1.4; max-width: 24ch; }
.lead-grid { display: grid; grid-template-columns: 0.9fr 1.1fr; gap: clamp(28px, 5vw, 64px); align-items: start; }
.lead-grid .body p + p { margin-top: 1.1em; }
.lead-grid .body p { color: var(--ink); }
@media (max-width: 760px) { .lead-grid { grid-template-columns: 1fr; gap: 28px; } }

/* ---------- Steps ---------- */
.steps { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1px; background: var(--line); border: 1px solid var(--line); }
.step { background: var(--paper); padding: clamp(24px, 3vw, 38px); }
.step .num { font-family: var(--mono); font-size: 0.78rem; color: var(--evergreen); letter-spacing: 0.1em; }
.step h3 { font-size: var(--step-1); margin: 16px 0 10px; }
.step p { color: var(--stone); font-size: var(--step--1); line-height: 1.55; }
.band .steps .step { background: var(--paper-2); }
@media (max-width: 760px) { .steps { grid-template-columns: 1fr; } }

/* ---------- Features ---------- */
.features { display: grid; grid-template-columns: repeat(2, 1fr); gap: 1px; background: var(--line); border: 1px solid var(--line); }
.feature { background: var(--paper); padding: clamp(24px, 3vw, 34px); }
.feature .ico { width: 28px; height: 28px; color: var(--evergreen); margin-bottom: 16px; }
.feature h3 { font-size: var(--step-1); margin-bottom: 8px; }
.feature p { color: var(--stone); font-size: var(--step--1); line-height: 1.55; }
@media (max-width: 680px) { .features { grid-template-columns: 1fr; } }

/* ---------- Sustainability ---------- */
.mission { display: grid; grid-template-columns: 1.1fr 0.9fr; gap: clamp(28px, 5vw, 64px); align-items: center; }
.mission .quote { font-family: var(--serif); font-size: var(--step-2); line-height: 1.4; }
.mission .quote span { color: var(--evergreen); }
.mission ul { list-style: none; padding: 0; margin-top: 6px; }
.mission li { padding: 16px 0; border-top: 1px solid var(--line); display: flex; gap: 14px; align-items: baseline; }
.mission li:last-child { border-bottom: 1px solid var(--line); }
.mission li .k { font-family: var(--mono); font-size: 0.72rem; color: var(--evergreen); letter-spacing: 0.08em; white-space: nowrap; }
.mission li .v { color: var(--ink); font-size: var(--step--1); }
@media (max-width: 760px) { .mission { grid-template-columns: 1fr; gap: 28px; } }

/* ---------- Safety teaser ---------- */
.safety-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: clamp(20px, 3vw, 36px); }
.safety-grid .item h3 { font-size: var(--step-1); margin-bottom: 8px; }
.safety-grid .item p { color: var(--stone); font-size: var(--step--1); line-height: 1.55; }
.safety-grid .item .bar { width: 32px; height: 2px; background: var(--evergreen); margin-bottom: 16px; }
@media (max-width: 760px) { .safety-grid { grid-template-columns: 1fr; gap: 24px; } }

/* ---------- CTA band ---------- */
.cta { background: var(--evergreen); color: #fff; }
.cta h2 { color: #fff; font-size: var(--step-3); max-width: 18ch; }
.cta p { color: color-mix(in srgb, #fff 75%, transparent); margin-top: 14px; max-width: 44ch; }
.cta .hero-actions { margin-top: 28px; }
.cta .btn-primary { background: var(--paper); color: var(--evergreen-deep); }
.cta .btn-primary:hover { background: #fff; }
.cta .btn-ghost { color: #fff; border-color: color-mix(in srgb, #fff 35%, transparent); }
.cta .btn-ghost:hover { border-color: #fff; }
.cta .hero-note { color: color-mix(in srgb, #fff 70%, transparent); }

/* ---------- Footer ---------- */
.site-footer { background: var(--ink); color: var(--paper); padding-block: clamp(48px, 6vw, 72px) 28px; }
.footer-top { display: grid; grid-template-columns: 1.4fr 1fr 1fr 1fr; gap: clamp(28px, 4vw, 48px); }
.footer-brand .name { font-family: var(--serif); font-size: 1.2rem; }
.footer-brand p { color: color-mix(in srgb, var(--paper) 60%, transparent); font-size: var(--step--1); margin-top: 12px; max-width: 32ch; }
.footer-col h4 { font-family: var(--mono); font-size: 0.7rem; letter-spacing: 0.12em; text-transform: uppercase; color: color-mix(in srgb, var(--paper) 55%, transparent); font-weight: 500; margin-bottom: 16px; }
.footer-col ul { list-style: none; padding: 0; }
.footer-col li { margin-bottom: 11px; }
.footer-col a { color: color-mix(in srgb, var(--paper) 82%, transparent); text-decoration: none; font-size: var(--step--1); transition: color .15s ease; }
.footer-col a:hover { color: #fff; }
.footer-bottom { display: flex; justify-content: space-between; align-items: center; flex-wrap: wrap; gap: 14px;
  margin-top: clamp(36px, 5vw, 56px); padding-top: 22px; border-top: 1px solid color-mix(in srgb, var(--paper) 18%, transparent); }
.footer-bottom p { color: color-mix(in srgb, var(--paper) 50%, transparent); font-size: 0.8rem; }
.footer-bottom .meta { font-family: var(--mono); font-size: 0.7rem; color: color-mix(in srgb, var(--paper) 42%, transparent); letter-spacing: 0.04em; }
@media (max-width: 760px) { .footer-top { grid-template-columns: 1fr 1fr; } .footer-brand { grid-column: 1 / -1; } }

/* ---------- Reveal on scroll ---------- */
.reveal { opacity: 0; transform: translateY(14px); transition: opacity .6s ease, transform .6s ease; }
.reveal.in { opacity: 1; transform: none; }
@media (prefers-reduced-motion: reduce) { .reveal { opacity: 1; transform: none; } }

/* ---------- Focus ---------- */
:focus-visible { outline: 2px solid var(--evergreen); outline-offset: 3px; border-radius: 2px; }
.cta :focus-visible, .site-footer :focus-visible { outline-color: var(--paper); }

/* ============================================================
   Document pages (privacy / terms / safety / support)
   ============================================================ */
.doc-hero { padding-top: clamp(44px, 6vw, 72px); padding-bottom: clamp(28px, 4vw, 40px); border-bottom: 1px solid var(--line); }
.doc-hero h1 { font-size: var(--step-3); margin-top: 16px; }
.doc-hero .updated { font-family: var(--mono); font-size: 0.74rem; color: var(--stone); margin-top: 16px; letter-spacing: 0.03em; }
.doc-layout { display: grid; grid-template-columns: 220px 1fr; gap: clamp(28px, 5vw, 64px); padding-block: clamp(40px, 5vw, 64px); align-items: start; }
.doc-toc { position: sticky; top: 90px; }
.doc-toc h4 { font-family: var(--mono); font-size: 0.7rem; letter-spacing: 0.12em; text-transform: uppercase; color: var(--stone); margin-bottom: 14px; font-weight: 500; }
.doc-toc ul { list-style: none; padding: 0; }
.doc-toc li { margin-bottom: 9px; }
.doc-toc a { text-decoration: none; color: var(--stone); font-size: 0.86rem; line-height: 1.4; transition: color .15s ease; }
.doc-toc a:hover { color: var(--evergreen); }
.doc-body { max-width: 70ch; }
.doc-body .summary {
  background: var(--sage); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 20px 22px; margin-bottom: 40px;
}
.doc-body .summary strong { font-family: var(--mono); font-size: 0.72rem; letter-spacing: 0.1em; text-transform: uppercase; color: var(--evergreen); display: block; margin-bottom: 8px; }
.doc-body .summary p { font-size: var(--step--1); color: var(--ink); }
.doc-body h2 { font-size: var(--step-2); margin: 44px 0 14px; scroll-margin-top: 90px; }
.doc-body h2:first-of-type { margin-top: 0; }
.doc-body h3 { font-size: var(--step-1); margin: 28px 0 10px; font-family: var(--serif); }
.doc-body p { margin-bottom: 1em; color: var(--ink); }
.doc-body ul, .doc-body ol { margin: 0 0 1.2em; padding-left: 1.3em; }
.doc-body li { margin-bottom: 0.5em; }
.doc-body a { color: var(--evergreen); text-underline-offset: 2px; }
.doc-body .note { font-size: var(--step--1); color: var(--stone); border-left: 2px solid var(--evergreen); padding-left: 16px; margin: 24px 0; }
@media (max-width: 860px) {
  .doc-layout { grid-template-columns: 1fr; }
  .doc-toc { position: static; border-bottom: 1px solid var(--line); padding-bottom: 24px; }
}

/* FAQ (support) */
.faq details { border-bottom: 1px solid var(--line); }
.faq summary { cursor: pointer; padding: 20px 0; font-family: var(--serif); font-size: var(--step-1); list-style: none; display: flex; justify-content: space-between; gap: 16px; align-items: baseline; }
.faq summary::-webkit-details-marker { display: none; }
.faq summary::after { content: "+"; font-family: var(--mono); color: var(--evergreen); font-size: 1.3rem; }
.faq details[open] summary::after { content: "–"; }
.faq details[open] summary { padding-bottom: 6px; }
.faq .answer { padding-bottom: 22px; color: var(--stone); max-width: 64ch; }
.faq .answer p + p { margin-top: 0.8em; }