/* Physics of Buildings home (brand hub). Builds on the brand layer's theme.css tokens; no colours of its own.
   The idiom is a drawing set's index: a heavy rule opens each group, every explainer is a sheet with its number,
   its drawing framed by a hairline, and the title set in the condensed display face. */

.hub { max-width: var(--wide); margin: 0 auto; padding: 0 var(--gutter); }

/* ---------------------------------------------------------------- title block */
.hub-head { padding: 1.4rem 0 1.5rem; }
.hub-head h1 { font-size: clamp(2.3rem, 9.2vw, 4.7rem); line-height: .98; margin: 0 0 .3em; max-width: 20ch; text-wrap: balance; }
.hub-head .dek { font: 400 clamp(1.08rem, 2.3vw, 1.36rem)/1.42 var(--font-serif); max-width: 34rem; margin: 0; color: var(--ink-soft); }
@media (min-width: 980px) { .hub-head { padding: 2.6rem 0 2.2rem; } .hub-head h1 { margin-bottom: .32em; } }

/* ---------------------------------------------------------------- groups */
.hub-group { margin: 0 0 2.4rem; }
.hub-group-head { border-top: 3px solid var(--ink); padding-top: .5rem; margin-bottom: 1rem;
  display: flex; flex-wrap: wrap; align-items: baseline; gap: .1rem 1rem; }
.hub-group-head h2 { border-top: 0; padding-top: 0; margin: 0; font-size: clamp(1.5rem, 3.6vw, 2.05rem); }
.hub-group-note { margin: 0; font: 400 1rem/1.4 var(--font-sans); color: var(--muted); }

/* ---------------------------------------------------------------- cards: one sheet each */
.hub-cards { list-style: none; margin: 0; padding: 0; display: grid; gap: 1.6rem; grid-template-columns: minmax(0, 1fr); }
@media (min-width: 640px) { .hub-cards { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 2.2rem 1.8rem; } }
.hub-card { position: relative; display: flex; flex-direction: column; margin: 0; }
.hub-card-fig { border: 1px solid var(--rule); background: var(--bg); line-height: 0; transition: border-color .15s; }
.hub-img img { display: block; width: 100%; height: auto; aspect-ratio: 3 / 2; }
.hub-img-dark { display: none; }
:root[data-theme="dark"] .hub-img-light { display: none; }
:root[data-theme="dark"] .hub-img-dark { display: block; }
.hub-card-text { display: grid; grid-template-columns: auto minmax(0, 1fr); gap: .1rem .75rem; padding-top: .7rem; align-items: baseline; }
.hub-sheet { grid-row: 1; margin: 0; font: 600 .9rem/1 var(--font-sans); font-variant-numeric: tabular-nums; color: var(--accent);
  border: 1px solid currentColor; padding: .28rem .38rem .24rem; position: relative; top: -.15rem; white-space: nowrap; }
.hub-card-title { grid-column: 2; margin: 0; padding: 0; border: 0; font: 700 clamp(1.28rem, 2.4vw, 1.5rem)/1.12 var(--font-cond); text-wrap: balance; }
.hub-card-link { color: var(--ink); text-decoration: none; }
.hub-card-link::after { content: ""; position: absolute; inset: 0; }
.hub-card-link:focus-visible { outline: none; }
.hub-card:has(.hub-card-link:focus-visible) { outline: 3px solid var(--focus); outline-offset: 4px; }
.hub-card-does { grid-column: 2; margin: .35rem 0 0; font: 400 1.02rem/1.45 var(--font-serif); color: var(--ink-soft); }
.hub-card:hover .hub-card-fig { border-color: var(--ink); }
.hub-card:hover .hub-card-link { text-decoration: underline; text-decoration-thickness: 2px; text-underline-offset: .14em; text-decoration-color: var(--accent); }

/* ---------------------------------------------------------------- how these are made */
.hub-more.prose { margin: 1rem 0 0; padding: 0; max-width: var(--prose); }
.hub-more h2 { font-size: clamp(1.35rem, 3vw, 1.6rem); }
.hub-more p { font-size: 1.05rem; }

@media (max-width: 639px) {
  .hub-head { padding: 1rem 0 1.2rem; }
  .hub-group-head { margin-bottom: .8rem; }
  .hub-card-does { font-size: 1rem; }
}
@media (prefers-reduced-motion: reduce) { .hub-card-fig { transition: none; } }
.site-footer .footer-h { font: 600 .95rem var(--font-sans); margin: 0 0 .4rem; color: var(--ink); }