/* Zapchat. The palette is the app's own: the green is the exact fill from the
   app icon (#25D366) and the dark ground is the icon's dark specialization
   (#111B21). Nothing here is invented — a product site that does not look like
   the product it sells is a second registry of the brand. */

:root {
  color-scheme: light dark;

  --green: #25d366;
  --link: #0a7c5a;          /* the green, darkened until it passes on white */
  --ground: #ffffff;
  --surface: #f4f7f5;       /* neutral, biased a few degrees toward the green */
  --line: #e2e8e4;
  --ink: #0e1512;
  --muted: #5d6c65;
  --shadow: 0 1px 2px rgba(14,21,18,.05), 0 8px 24px rgba(14,21,18,.06);
}

/* Only the tokens change. Every rule below reads them, so a colour is never
   defined solely inside a media query — that is how a page ends up rendering
   one theme's text on the other theme's ground. */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --link: #4ee39a;
    --ground: #111b21;
    --surface: #1a262d;
    --line: #26343c;
    --ink: #e9edeb;
    --muted: #93a5ad;
    --shadow: 0 1px 2px rgba(0,0,0,.3), 0 8px 24px rgba(0,0,0,.35);
  }
}
:root[data-theme="dark"] {
  --link: #4ee39a;
  --ground: #111b21;
  --surface: #1a262d;
  --line: #26343c;
  --ink: #e9edeb;
  --muted: #93a5ad;
  --shadow: 0 1px 2px rgba(0,0,0,.3), 0 8px 24px rgba(0,0,0,.35);
}

* { box-sizing: border-box; }

body {
  margin: 0;
  padding: 3.5rem 1.25rem 4rem;
  font: 17px/1.6 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  color: var(--ink);
  background: var(--ground);
  -webkit-font-smoothing: antialiased;
}

/* One column for prose. The screenshot rail below breaks out of it on purpose. */
.wrap { max-width: 44rem; margin: 0 auto; }

h1 { font-size: clamp(2.1rem, 7vw, 2.9rem); line-height: 1.1; letter-spacing: -.03em;
     margin: 0 0 .4rem; text-wrap: balance; }
h2 { font-size: 1.2rem; letter-spacing: -.01em; margin: 3rem 0 .6rem; text-wrap: balance; }
h3 { font-size: 1rem; margin: 1.75rem 0 .35rem; }
p  { margin: 0 0 1rem; }
.sub { color: var(--muted); font-size: 1.12rem; margin: 0 0 1.75rem; text-wrap: balance; }
.lede { font-size: 1.06rem; }
a { color: var(--link); text-underline-offset: .18em; }
a:focus-visible, summary:focus-visible { outline: 2px solid var(--green); outline-offset: 3px; border-radius: 4px; }
strong { font-weight: 600; }

/* Header */
.mark { width: 76px; height: 76px; border-radius: 22%; display: block; margin: 0 0 1.1rem; }

/* Screenshots. Full-bleed and scrollable so a phone never has to shrink four
   portrait screens into a row it cannot read. */
.shots {
  display: flex; gap: 1rem; overflow-x: auto;
  /* Full-bleed so a narrow screen can scroll the row edge to edge, but
     centred whenever the four fit — "safe" so centring never pushes the first
     one out of reach on the left, which is what plain centre does. */
  margin: 2rem calc(50% - 50vw) 0;
  padding: .5rem 1.25rem 1.25rem;
  justify-content: safe center;
  scroll-snap-type: x mandatory; -webkit-overflow-scrolling: touch;
  scrollbar-width: thin;
}
.shots figure { margin: 0; flex: 0 0 auto; width: 216px; scroll-snap-align: center; }
.shots img {
  width: 100%; height: auto; display: block; border-radius: 22px;
  border: 1px solid var(--line); box-shadow: var(--shadow); background: var(--surface);
}
.shots figcaption { color: var(--muted); font-size: .85rem; margin-top: .6rem; text-align: center; }

/* An aside under a block, not a section subtitle. */
.note { color: var(--muted); font-size: .95rem; margin: .25rem 0 0; }

/* Steps. Numbered because this IS a sequence — do them out of order and the
   code has expired before you reach WhatsApp. */
ol.steps { margin: 0; padding: 0; list-style: none; counter-reset: step; }
ol.steps li {
  counter-increment: step; position: relative; padding: 0 0 1.1rem 2.6rem;
}
ol.steps li::before {
  content: counter(step); position: absolute; left: 0; top: .05rem;
  width: 1.7rem; height: 1.7rem; border-radius: 50%;
  background: var(--green); color: #062b16;
  font-size: .85rem; font-weight: 700; display: grid; place-items: center;
}
ol.steps b { font-weight: 600; }

/* Two short lists side by side where there is room. */
.pair { display: grid; gap: 1.25rem 2.5rem; grid-template-columns: 1fr; }
@media (min-width: 34rem) { .pair { grid-template-columns: 1fr 1fr; } }
.pair h3 { margin-top: 0; }
.pair p { color: var(--muted); margin: 0; }

/* FAQ */
details {
  border-top: 1px solid var(--line); padding: .9rem 0;
}
details:last-of-type { border-bottom: 1px solid var(--line); }
summary {
  cursor: pointer; font-weight: 600; list-style: none; display: flex;
  justify-content: space-between; align-items: center; gap: 1rem;
}
summary::-webkit-details-marker { display: none; }
summary::after {
  content: "+"; color: var(--muted); font-weight: 400; font-size: 1.3rem; line-height: 1;
}
details[open] summary::after { content: "\2212"; }
details p { margin: .7rem 0 .2rem; color: var(--muted); }
details p:last-child { margin-bottom: 0; }

/* Footer */
nav { margin-top: 3.5rem; padding-top: 1.5rem; border-top: 1px solid var(--line);
      font-size: .93rem; }
.fine { font-size: .82rem; color: var(--muted); margin-top: 1.5rem; }
.fine a { color: inherit; }

@media (prefers-reduced-motion: reduce) {
  * { animation: none !important; transition: none !important; scroll-behavior: auto !important; }
}