/* ==========================================================================
   BASE — reset, typography, blueprint grid-paper backdrop
   ========================================================================== */

*, *::before, *::after{ box-sizing: border-box; }
html{ scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body{
  margin: 0;
  font-family: var(--font-body);
  font-size: var(--step-2);
  line-height: 1.6;
  color: var(--ink);
  background: var(--paper);
  /* faint drafting-grid backdrop, mobile-safe (fixed can jank on iOS, so scroll) */
  background-image:
    linear-gradient(var(--paper-line) 1px, transparent 1px),
    linear-gradient(90deg, var(--paper-line) 1px, transparent 1px);
  background-size: 32px 32px;
}
img{ max-width: 100%; display: block; }
a{ color: var(--blue-deep); text-decoration-thickness: 1.5px; text-underline-offset: 3px; }
a:hover{ color: var(--blue); }
h1,h2,h3,h4{
  font-family: var(--font-display);
  color: var(--ink);
  line-height: 1.08;
  margin: 0 0 var(--space-2);
  font-weight: 600;
}
h1{ font-size: var(--step-6); letter-spacing: -0.01em; }
h2{ font-size: var(--step-5); letter-spacing: -0.01em; }
h3{ font-size: var(--step-4); }
p{ margin: 0 0 var(--space-2); color: var(--ink-soft); max-width: 60ch; }
.lead{ font-size: var(--step-3); color: var(--ink); }

/* visible focus ring everywhere — no outline: none without a replacement */
:focus-visible{
  outline: 2.5px solid var(--annotation);
  outline-offset: 3px;
}

.container{
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

.mono-label{
  font-family: var(--font-mono);
  font-size: var(--step-0);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--blue-deep);
  display: inline-flex;
  align-items: center;
  gap: 0.5em;
}
.mono-label::before{ content: ""; width: 22px; height: 1px; background: currentColor; display: inline-block; }

.visually-hidden{
  position: absolute; width: 1px; height: 1px; overflow: hidden;
  clip: rect(0 0 0 0); white-space: nowrap; border: 0; padding: 0; margin: -1px;
}

.skip-link{
  position: absolute; left: 1rem; top: -100px;
  background: var(--ink); color: var(--white);
  padding: 0.75rem 1.25rem; z-index: 200; transition: top var(--dur) var(--ease);
}
.skip-link:focus{ top: 1rem; }

section{ padding-block: var(--space-6); position: relative; }
.section-head{ max-width: 62ch; margin-bottom: var(--space-4); }

/* section number ticks — used only where sections form an actual sequence
   (see .process), not as decoration on every heading */
.tick-row{ display: flex; align-items: center; gap: var(--space-2); margin-bottom: var(--space-2); }