/* ============================================================
   Haenginro Lab — shell.css
   Shared shell for every page on haenginro.com.

   Scope (fixed): font loading, top brand bar, footer, brand mark.
   NOT in scope: color themes, layout grids, component styles —
   those live in each page's own files. If it's in this file it
   is shell; if it's in the page file it is product personality.

   Canonical markup — paste as-is, do not restyle .shell-*
   selectors. A page MAY add its own class next to shell-top
   (background, sticky) and its own elements inside
   shell-top-inner (e.g. a nav), styled by its own CSS:

   <header class="shell-top">
     <div class="shell-top-inner">
       <a class="shell-brand" href="/">
         <span class="shell-brand-mark" aria-hidden="true"></span>
         <span>Haenginro Lab</span>
       </a>
       <!-- optional page-owned elements -->
     </div>
   </header>

   ...page content (product nav may sit below the shell bar)...

   <footer class="shell-footer">
     <a class="shell-back" href="/">&larr; Back to Haenginro Lab</a>
     <span class="shell-copy">&copy; 2026 Haenginro Lab. All rights reserved.</span>
   </footer>
   ============================================================ */

/* Lab typeface — Inter, self-hosted variable font (100–900).
   Latin subset + arrows (U+2190-2199), ~113KB, axes preserved.
   Rules:
   - /fonts/* is cached immutable for a year (_headers) — any font
     change MUST ship under a new filename.
   - Product pages must NOT <link rel="preload"> this font: there
     Inter is shell-only (nav/footer) and preloading would compete
     with the product's own fonts. Root preloads it (body typeface).
   - Regenerate: pyftsubset with the unicode ranges above. */
@font-face {
  font-family: "Inter";
  src: url("/fonts/InterVariable.woff2") format("woff2");
  font-weight: 100 900;
  font-style: normal;
  font-display: swap;
}

/* ── Top brand bar ──────────────────────────────────────────
   Text color inherits from the page; hairlines derive from
   currentColor so the bar sits on any light or dark theme. */

.shell-top {
  font-family: "Inter", ui-sans-serif, system-ui, -apple-system, sans-serif;
  border-bottom: 1px solid color-mix(in srgb, currentColor 14%, transparent);
}

.shell-top-inner {
  width: min(1120px, calc(100% - 40px));
  margin: 0 auto;
  height: 64px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
}

.shell-brand {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 15px;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: inherit;
  text-decoration: none;
}

/* Brand mark — fixed lab identity, identical on every page */
.shell-brand-mark {
  width: 28px;
  height: 28px;
  border-radius: 9px;
  background: linear-gradient(135deg, rgb(16, 91, 216), rgb(6, 31, 74));
  border: 1px solid rgba(255, 255, 255, 0.18);
  position: relative;
  flex: none;
}

.shell-brand-mark::after {
  content: "";
  position: absolute;
  width: 9px;
  height: 9px;
  border: 2px solid #fff;
  border-left: 0;
  border-bottom: 0;
  top: 8px;
  left: 7px;
  transform: rotate(45deg);
  opacity: 0.9;
}

/* ── Footer ───────────────────────────────────────────────── */

.shell-footer {
  font-family: "Inter", ui-sans-serif, system-ui, -apple-system, sans-serif;
  border-top: 1px solid color-mix(in srgb, currentColor 14%, transparent);
  width: min(1120px, calc(100% - 40px));
  margin: 0 auto;
  padding: 28px 0 36px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
  font-size: 13px;
}

.shell-footer .shell-back {
  color: inherit;
  text-decoration: none;
  font-weight: 500;
}

.shell-footer .shell-back:hover {
  text-decoration: underline;
}

.shell-footer .shell-copy {
  opacity: 0.65;
}