/* Base reset */
* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
:focus { outline: 3px solid; outline-offset: 2px; }

/* Color systems via CSS variables */
:root {
  /* Section colors */
  --container-bg: #ffffff;
  --container-fg: #111111;

  --header-bg: #f7f7f7;
  --header-fg: #0a0a0a;

  --main-bg: #ffffff;
  --main-fg: #111111;

  --footer-bg: #f1f1f1;
  --footer-fg: #0a0a0a;

  --link: #0645ad;
  --link-visited: #0b0080;
  --border: #d9d9d9;
}

/* Auto theme follows user OS unless overridden */
@media (prefers-color-scheme: dark) {
  [data-theme="auto"] {
    --container-bg: #0f1115;
    --container-fg: #f0f3f6;

    --header-bg: #131620;
    --header-fg: #f6f8fa;

    --main-bg: #0f1115;
    --main-fg: #f0f3f6;

    --footer-bg: #131620;
    --footer-fg: #f6f8fa;

    --link: #6ea8fe;
    --link-visited: #b197fc;
    --border: #2a2f3a;
  }
}

/* Explicit light */
[data-theme="light"] {
  --container-bg: #ffffff;
  --container-fg: #111111;

  --header-bg: #f7f7f7;
  --header-fg: #0a0a0a;

  --main-bg: #ffffff;
  --main-fg: #111111;

  --footer-bg: #f1f1f1;
  --footer-fg: #0a0a0a;

  --link: #0645ad;
  --link-visited: #0b0080;
  --border: #d9d9d9;
}

/* Explicit dark */
[data-theme="dark"] {
  --container-bg: #0f1115;
  --container-fg: #f0f3f6;

  --header-bg: #131620;
  --header-fg: #f6f8fa;

  --main-bg: #0f1115;
  --main-fg: #f0f3f6;

  --footer-bg: #131620;
  --footer-fg: #f6f8fa;

  --link: #6ea8fe;
  --link-visited: #b197fc;
  --border: #2a2f3a;
}

/* Global element colors */
body { background: var(--container-bg); color: var(--container-fg); line-height: 1.6; font-family: system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, sans-serif; }
a { color: var(--link); }
a:visited { color: var(--link-visited); }
hr { border: 0; border-top: 1px solid var(--border); }

/* Layout wrappers */
.container { padding: 1rem; margin: 0 auto; max-width: 1200px; }
.site-header { background: var(--header-bg); color: var(--header-fg); border-bottom: 1px solid var(--border); display: flex; align-items: center; justify-content: space-between; padding: .75rem 1rem; position: sticky; top: 0; z-index: 1000; }
.site-footer { background: var(--footer-bg); color: var(--footer-fg); border-top: 1px solid var(--border); padding: 1rem; text-align: center; }

main { background: var(--main-bg); color: var(--main-fg); padding: 1rem; }

/* Branding */
.brand { display: flex; align-items: center; gap: .5rem; }
.logo { width: 44px; height: 44px; object-fit: contain; }
.brand-title { font-weight: 700; letter-spacing: .05em; white-space: nowrap; }

/* Navigation */
.nav-toggle { display: none; border: 1px solid var(--border); background: transparent; padding: .5rem .75rem; border-radius: .5rem; color: inherit; }
.site-nav { margin-left: 1rem; }
.menu-root, .submenu { list-style: none; margin: 0; padding: 0; }
.menu-root { display: flex; gap: 1rem; align-items: center; }
.menu-root > li { position: relative; }
.menu-root a, .menu-root button.submenu-toggle, .submenu button { background: none; border: none; color: inherit; font: inherit; cursor: pointer; padding: .5rem .25rem; }
.menu-root a:hover, .menu-root button:hover, .submenu a:hover, .submenu button:hover { text-decoration: underline; }

/* Submenus */
.has-submenu .submenu { position: absolute; top: 100%; right: 0; min-width: 200px; background: var(--main-bg); color: var(--main-fg); border: 1px solid var(--border); padding: .5rem; border-radius: .5rem; display: none; }
.has-submenu.open > .submenu { display: block; }
.submenu li { padding: .25rem 0; }

/* Responsive: hamburger */
@media (max-width: 860px) {
  .nav-toggle { display: inline-block; }
  .site-nav { display: none; width: 100%; }
  .site-header { flex-wrap: wrap; gap: .5rem; }
  .site-nav.open { display: block; }
  .menu-root { flex-direction: column; align-items: flex-start; gap: .25rem; }
  .has-submenu .submenu { position: static; border: none; padding-left: 1rem; }
}

/* Skip link */
.skip-link {
  position: absolute; left: -9999px; top: auto; width: 1px; height: 1px; overflow: hidden;
}
.skip-link:focus {
  position: static; width: auto; height: auto; padding: .5rem; background: var(--header-bg); border: 2px solid var(--border);
}