/* ===================================================================
   layout.css — page structure, single 640px column, mobile-first
   Spec: lander-build-prompt_v1.md §2 (layout) + §3 (architecture)
   =================================================================== */

/* ---- the column ---- */
.col {
  width: 100%;
  max-width: var(--col);
  margin-inline: auto;
  padding-inline: var(--pad-mobile);
}
@media (min-width: 641px) { .col { padding-inline: var(--pad-tablet); } }
@media (min-width: 720px) { .col { padding-inline: 0; } } /* 640 column self-spaces */

/* ---- top bar (wordmark only — no nav/login/search) ---- */
.topbar {
  border-bottom: 1px solid var(--rule);
  background: var(--bg);
}
.topbar .col {
  display: flex;
  align-items: center;
  height: 56px;
}
.logo {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  text-decoration: none;
  line-height: 1;
}
.logo svg { display: block; flex: none; }
.logo-wordmark {
  font-weight: 600;
  font-size: 18px;
  color: var(--navy);
  letter-spacing: -0.01em;
}

/* ---- sticky condensed header (fades in on scroll) ---- */
.sticky-bar {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 50;
  background: var(--bg);
  border-bottom: 1px solid var(--rule);
  opacity: 0;
  transform: translateY(-100%);
  transition: opacity .25s ease, transform .25s ease;
  pointer-events: none;
}
.sticky-bar.is-visible {
  opacity: 1;
  transform: translateY(0);
  pointer-events: auto;
}
.sticky-bar .col {
  display: flex;
  align-items: center;
  height: 44px;
}
.sticky-bar .sticky-text {
  font-size: 13px;
  color: var(--muted);
  font-weight: 500;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

/* ---- byline strip ---- */
.byline {
  font-size: var(--fs-byline);
  color: var(--muted);
  margin-top: 40px;
  margin-bottom: 24px;
}

/* ---- H1 (Hannah's first message as headline) ---- */
.h1 { margin: 0 0 var(--sp-para); }
.h1-line1 {
  display: block;
  font-size: var(--fs-h1-1);
  font-weight: 600;
  line-height: var(--lh-h1);
  color: var(--ink);
  margin-bottom: 12px;
  letter-spacing: -0.01em;
}
.h1-line2 {
  display: block;
  font-size: var(--fs-h1-2);
  font-weight: 500;
  line-height: var(--lh-h1);
  color: var(--ink);
}

/* ---- intro paragraph ---- */
.intro p { margin: 0 0 var(--sp-para); }
.intro p:last-child { margin-bottom: 0; }

/* ---- section rhythm ---- */
section { margin-top: var(--sp-section); }
.section-chat {
  margin-top: var(--sp-chat);
  margin-bottom: var(--sp-chat);
}

h2.h2 {
  font-size: var(--fs-h2);
  font-weight: 600;
  line-height: var(--lh-h2);
  color: var(--ink);
  margin: 0 0 var(--sp-para);
  letter-spacing: -0.01em;
}

/* ---- footer ---- */
.footer {
  margin-top: var(--sp-section);
  padding-block: 40px 56px;
  border-top: 1px solid var(--rule);
}
.footer p {
  font-size: 12px;
  line-height: 1.6;
  color: var(--muted);
  margin: 0 0 12px;
}
.footer p:last-child { margin-bottom: 0; }