/* Layout: containers, grids, sections — editorial rhythm */

.container { width: 100%; margin-inline: auto; padding-inline: var(--gutter); }
.container--sm { max-width: var(--container-sm); }
.container--md { max-width: var(--container-md); }
.container--lg { max-width: var(--container-lg); }
.container--xl { max-width: var(--container-xl); }

/* Section system */
.section { padding-block: var(--section-pad); position: relative; }
.section--sm { padding-block: var(--section-pad-sm); }
.section--alt { background: var(--surface-alt); }
.section--dark { background: var(--surface-dark); color: var(--text-on-dark); }
.section--paper { background: var(--surface-page); }
.section--ruled { border-top: var(--border-soft); }

.section__header {
  display: grid;
  gap: var(--space-16);
  margin-bottom: clamp(2.5rem, 5vw, 4.5rem);
  max-width: var(--container-md);
}
.section__index {
  display: flex; align-items: baseline; gap: var(--space-16);
  border-top: var(--border-thin);
  padding-top: var(--space-16);
}
.section__index .spec-num { flex: none; }
.section__title { max-width: 22ch; }
.section__lede { max-width: var(--content-measure); }

/* Editorial grids */
.grid { display: grid; gap: var(--grid-gap); }
.grid--2 { grid-template-columns: 1fr; }
.grid--3 { grid-template-columns: 1fr; }
.grid--12 { grid-template-columns: 1fr; }
.split { display: grid; gap: clamp(2rem, 4vw, 4rem); grid-template-columns: 1fr; }

@media (min-width: 900px) {
  .grid--2 { grid-template-columns: repeat(2, 1fr); }
  .grid--3 { grid-template-columns: repeat(3, 1fr); }
  .split { grid-template-columns: 0.9fr 1.1fr; align-items: start; }
  .split--reverse > :first-child { order: 2; }
  .grid--12 { grid-template-columns: repeat(12, 1fr); }
  .span-4 { grid-column: span 4; }
  .span-5 { grid-column: span 5; }
  .span-6 { grid-column: span 6; }
  .span-7 { grid-column: span 7; }
  .span-8 { grid-column: span 8; }
}

/* Asymmetric editorial offset */
@media (min-width: 900px) {
  .offset-a { padding-left: clamp(0rem, 4vw, 3rem); }
  .offset-b { margin-top: 3.5rem; }
}

/* Fine-rule rows (service items, list rows) */
.rule-list { border-top: var(--border-thin); }
.rule-row {
  display: grid; gap: 0.75rem;
  padding: clamp(1.5rem, 3vw, 2.25rem) 0;
  border-bottom: var(--border-thin);
}
@media (min-width: 900px) {
  .rule-row { grid-template-columns: 64px 1fr 1.2fr auto; align-items: baseline; gap: 2rem; }
}

/* Sticky note column */
@media (min-width: 900px) {
  .sticky { position: sticky; top: calc(var(--header-h) + 24px); }
}

/* Hairline frame for interface fragments / diagrams */
.frame {
  border: var(--border-thin);
  background: var(--color-paper);
  border-radius: var(--radius-card);
  box-shadow: var(--shadow-xs);
  overflow: hidden;
}
.frame--dark { background: var(--color-navy-soft); border-color: var(--line-on-dark-soft); }
.frame__bar {
  display: flex; align-items: center; gap: 8px;
  padding: 10px 14px; border-bottom: var(--border-soft);
  font-family: var(--font-mono); font-size: var(--fs-mono-sm); color: var(--text-muted);
}
.dot { width: 8px; height: 8px; border-radius: 50%; background: var(--color-blue-gray); opacity: 0.7; }
.dot--accent { background: var(--accent); opacity: 1; }
.frame__body { padding: clamp(1.25rem, 3vw, 2rem); }