/* Frontier: a visual opening and a readable, numbered development story. */
.frontier-tabs { background: var(--paper-2); border-bottom: 1px solid var(--rule); }
.frontier-tabs .wrap { display: flex; align-items: stretch; gap: 32px; }
.frontier-tabs span { align-self: center; margin-right: auto; color: var(--ink-3); font-size: 11px; text-transform: uppercase; letter-spacing: .09em; }
.frontier-tabs a { color: var(--ink-2); font-size: 14px; padding: 17px 0 14px; border-bottom: 3px solid transparent; }
.frontier-tabs a[aria-current="page"] { color: var(--accent); border-color: var(--accent); font-weight: 600; }
.frontier-tabs a:hover { color: var(--accent); }
@media (max-width: 540px) { .frontier-tabs span { display: none; } .frontier-tabs .wrap { gap: 28px; } }
.frontier-page h1, .frontier-page h2 { font-family: var(--sans); font-weight: 500; }
.frontier-hero { background: #1c2428; color: #e2e5e3; padding: 76px 0 72px; }
.frontier-hero-grid { display: grid; grid-template-columns: 1.2fr 1fr; gap: 70px; align-items: center; }
.frontier-hero .eyebrow { color: #dcae8d; }
.frontier-hero h1 { color: #faf7ef; font-size: clamp(44px, 5.2vw, 68px); line-height: 1.06; letter-spacing: -.045em; }
.frontier-deck { font-size: 18px; line-height: 1.7; max-width: 520px; margin-top: 28px; }
.frontier-hero-link { display: inline-flex; gap: 24px; margin-top: 30px; color: #f0c5a5; font-size: 14px; text-decoration: underline; text-underline-offset: 5px; }
.frontier-hero-link:hover { color: white; }
.frontier-context { display: grid; grid-template-columns: 1fr .65fr 1.3fr; gap: 35px; padding-top: 30px; padding-bottom: 30px; border-bottom: 1px solid var(--rule); }
.frontier-context p { margin: 0; font-size: 14px; color: var(--ink); }
.frontier-context span { display: block; font-size: 11px; letter-spacing: .09em; text-transform: uppercase; color: var(--accent); margin-bottom: 8px; }
.frontier-layout { display: grid; grid-template-columns: 220px minmax(0, 1fr); gap: 65px; align-items: start; padding-top: 64px; padding-bottom: 70px; }
.frontier-toc { position: sticky; top: 96px; }
.frontier-toc .eyebrow { margin-bottom: 12px; }
.frontier-toc a { display: flex; gap: 14px; padding: 12px 0; border-bottom: 1px solid var(--rule); color: var(--ink-2); font-size: 13px; }
.frontier-toc a:hover { color: var(--accent); }
.frontier-toc a span { color: var(--accent); font-size: 11px; padding-top: 2px; }
.frontier-article { min-width: 0; }
.frontier-intro { padding-bottom: 38px; }
.frontier-article p { line-height: 1.8; }
.frontier-chapter { padding: 36px 0 42px; border-top: 1px solid var(--rule); border-bottom: none; scroll-margin-top: 85px; }
.frontier-chapter .chapter-number { color: var(--accent); font-size: 11px; letter-spacing: .08em; text-transform: uppercase; margin-bottom: 12px; }
.frontier-chapter h2 { font-size: clamp(25px, 2.8vw, 32px); line-height: 1.25; margin-bottom: 22px; }
.frontier-purpose { background: var(--paper-2); border-top: 3px solid var(--accent); padding: 30px; margin-top: 10px; }
.frontier-next { display: flex; flex-wrap: wrap; gap: 16px 26px; padding-top: 32px; font-size: 14px; }
.frontier-next a { text-decoration: underline; text-underline-offset: 4px; }
.frontier-page a:focus-visible { outline: 2px solid currentColor; outline-offset: 5px; }
@media (max-width: 960px) {
  .frontier-hero-grid { gap: 32px; }
  .frontier-layout { grid-template-columns: minmax(0, 1fr); gap: 36px; max-width: 780px; }
  .frontier-toc { position: static; display: grid; grid-template-columns: 1fr 1fr; gap: 0 28px; }
  .frontier-toc .eyebrow { grid-column: 1 / -1; }
}
@media (max-width: 680px) {
  .frontier-hero { padding: 46px 0; }
  .frontier-hero-grid { grid-template-columns: minmax(0, 1fr); gap: 36px; }
  .frontier-context { grid-template-columns: 1fr 1fr; gap: 22px; }
  .frontier-context p:last-child { grid-column: 1 / -1; }
  .frontier-layout { padding-top: 36px; }
  .frontier-purpose { padding: 24px 20px; }
}