/* =============================================================================
 * layout.css — page chrome: nav, footer, containers, grids, responsive
 * ===========================================================================*/

/* ---- Skip link ---- */
.skip-link {
  position: absolute; left: 8px; top: -48px; z-index: 200;
  background: var(--accent); color: #1a1a1a; padding: 8px 14px;
  border-radius: var(--radius-sm); font-weight: 600; transition: top .15s;
}
.skip-link:focus { top: 8px; }

/* ---- Top navigation (injected by ui.js) ---- */
.site-nav {
  position: sticky; top: 0; z-index: 100;
  background: var(--primary); color: #fff;
  box-shadow: var(--shadow);
}
.site-nav .nav-inner {
  max-width: var(--maxw); margin: 0 auto; padding: 0 18px;
  display: flex; align-items: center; gap: 8px; min-height: var(--nav-h);
}
.nav-brand {
  display: flex; align-items: center; gap: 10px;
  color: #fff; font-weight: 700; font-size: 1.05rem; white-space: nowrap;
}
.nav-brand:hover { text-decoration: none; }
.nav-brand .flask { width: 26px; height: 26px; flex: 0 0 auto; }
.nav-links { display: flex; align-items: center; gap: 2px; margin-left: auto; flex-wrap: wrap; }
.nav-links a, .nav-dd > button {
  color: #dcebef; background: transparent; border: 0; cursor: pointer;
  font: inherit; padding: 8px 12px; border-radius: var(--radius-sm);
  display: inline-block; white-space: nowrap;
}
.nav-links a:hover, .nav-dd > button:hover { background: rgba(255,255,255,.12); color: #fff; text-decoration: none; }
.nav-links a.active { background: var(--accent); color: #1a1a1a; font-weight: 600; }

/* Dropdown */
.nav-dd { position: relative; }
.nav-dd-menu {
  position: absolute; right: 0; top: calc(100% + 6px); min-width: 260px;
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); box-shadow: var(--shadow-lg);
  padding: 6px; display: none; flex-direction: column; z-index: 120;
}
.nav-dd.open .nav-dd-menu { display: flex; }
.nav-dd-menu a {
  color: var(--ink); padding: 9px 12px; border-radius: var(--radius-sm);
  display: flex; gap: 10px; align-items: baseline;
}
.nav-dd-menu a:hover { background: var(--panel); text-decoration: none; }
.nav-dd-menu a .num { color: var(--accent); font-weight: 700; font-family: var(--font-mono); }
.nav-dd-menu a small { display: block; color: var(--muted); }

.theme-toggle { font-size: 1.1rem; line-height: 1; }

/* Mobile nav toggle */
.nav-burger { display: none; margin-left: auto; background: transparent; border: 0; color: #fff; font-size: 1.5rem; cursor: pointer; padding: 6px 10px; }
@media (max-width: 880px) {
  .nav-burger { display: block; }
  .nav-links {
    display: none; position: absolute; top: var(--nav-h); left: 0; right: 0;
    background: var(--primary); flex-direction: column; align-items: stretch;
    padding: 8px; gap: 2px; box-shadow: var(--shadow-lg);
  }
  .site-nav.open .nav-links { display: flex; }
  .nav-dd-menu { position: static; box-shadow: none; border: 0; background: rgba(255,255,255,.06); }
  .nav-dd-menu a { color: #dcebef; }
  .nav-dd-menu a small { color: #aac6cd; }
}

/* ---- Page container ---- */
.container { max-width: var(--maxw); margin: 0 auto; padding: 28px 18px 60px; }
main { min-height: 60vh; }

/* Hero */
.hero {
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  color: #fff; padding: 54px 18px;
}
.hero-inner { max-width: var(--maxw); margin: 0 auto; }
.hero h1 { color: #fff; font-size: 2.4rem; margin: 0 0 10px; }
.hero p { color: #e6f0f3; font-size: 1.15rem; max-width: 720px; }
.hero .pill {
  display: inline-block; background: rgba(255,255,255,.16); color: #fff;
  border-radius: 999px; padding: 4px 14px; font-size: .85rem; margin-bottom: 16px;
}
.hero .cta-row { margin-top: 22px; display: flex; gap: 12px; flex-wrap: wrap; }

/* Breadcrumb */
.breadcrumb { color: var(--muted); font-size: .9rem; margin-bottom: 4px; }
.breadcrumb a { color: var(--muted); }

/* ---- Card grid ---- */
.grid { display: grid; gap: 18px; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); margin: 22px 0; }
.card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 20px; box-shadow: var(--shadow);
  display: flex; flex-direction: column;
}
.card h3 { margin-top: 0; }
.card .card-icon { font-size: 1.8rem; margin-bottom: 6px; }
.card .tag { font-size: .78rem; color: var(--accent-2); font-weight: 600; text-transform: uppercase; letter-spacing: .04em; }
a.card { color: inherit; } a.card:hover { text-decoration: none; box-shadow: var(--shadow-lg); transform: translateY(-2px); }
@media (prefers-reduced-motion: reduce) { a.card:hover { transform: none; } }
.card .card-cta { margin-top: auto; color: var(--primary-light); font-weight: 600; padding-top: 10px; }

/* Two-column experiment layout: controls | visualization */
.lab { display: grid; grid-template-columns: minmax(280px, 380px) 1fr; gap: 22px; align-items: start; }
@media (max-width: 860px) { .lab { grid-template-columns: 1fr; } }
.lab-panel { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 18px; box-shadow: var(--shadow); }
.lab-stage { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 18px; box-shadow: var(--shadow); min-height: 320px; }

/* Prose readability for theory pages */
.prose { max-width: 760px; }
.prose ul, .prose ol { padding-left: 1.3em; }
.prose li { margin: 0.35em 0; }
.section-card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 22px 26px; box-shadow: var(--shadow);
  margin: 18px 0;
}

/* ---- Prev / Next pager ---- */
.pager { display: flex; justify-content: space-between; gap: 12px; margin-top: 40px; padding-top: 18px; border-top: 1px solid var(--border); }
.pager a { display: inline-flex; flex-direction: column; padding: 10px 16px; border: 1px solid var(--border); border-radius: var(--radius); background: var(--surface); max-width: 48%; }
.pager a:hover { text-decoration: none; border-color: var(--primary-light); box-shadow: var(--shadow); }
.pager a.next { text-align: right; margin-left: auto; }
.pager small { color: var(--muted); }
.pager .lbl { color: var(--primary); font-weight: 600; }

/* ---- Footer ---- */
.site-footer { background: var(--primary); color: #cfe0e5; margin-top: 40px; }
.site-footer .foot-inner { max-width: var(--maxw); margin: 0 auto; padding: 22px 18px; display: flex; justify-content: space-between; gap: 12px; flex-wrap: wrap; font-size: .9rem; }
.site-footer a { color: #fff; }