/* ops37-dark theme — dark color scheme, system font, responsive, accessible */

*, *::before, *::after {
  box-sizing: border-box;
}

:root {
  --color-bg: #0f1117;
  --color-surface: #1a1d27;
  --color-text: #e8eaf0;
  --color-muted: #9099b0;
  --color-accent: #7eb8f7;
  --color-accent-hover: #a8d0ff;
  --color-border: #2d3147;
  --color-header-bg: #1a1d27;
  --color-footer-bg: #1a1d27;
  --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --font-size-base: 1rem;
  --line-height: 1.7;
  --max-width: 860px;
  --spacing: 1.5rem;
}

html {
  font-size: 16px;
}

body {
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  line-height: var(--line-height);
  color: var(--color-text);
  background-color: var(--color-bg);
  margin: 0;
  padding: 0;
}

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--spacing);
}

a {
  color: var(--color-accent);
  text-decoration: underline;
}

a:hover,
a:focus {
  color: var(--color-accent-hover);
}

a.skip-link {
  position: absolute;
  top: -40px;
  left: 0;
  background: var(--color-accent);
  color: #000;
  padding: 0.5rem 1rem;
  text-decoration: none;
  z-index: 100;
}

a.skip-link:focus {
  top: 0;
}

.site-header {
  background: var(--color-header-bg);
  border-bottom: 1px solid var(--color-border);
  padding: 0.75rem 0;
}

.site-header .container {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
}

.site-title {
  font-size: 1.25rem;
  font-weight: 700;
  text-decoration: none;
  color: var(--color-accent);
  flex-shrink: 0;
}

.main-nav ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  gap: 1.25rem;
  flex-wrap: wrap;
}

.main-nav a {
  text-decoration: none;
  color: var(--color-text);
  font-weight: 500;
}

.main-nav a:hover,
.main-nav a:focus,
.main-nav a[aria-current="page"] {
  color: var(--color-accent);
  text-decoration: underline;
}

.lang-switcher {
  margin-left: auto;
  font-size: 0.875rem;
}

.lang-switcher a {
  text-decoration: none;
  padding: 0.2rem 0.5rem;
  border: 1px solid var(--color-border);
  border-radius: 3px;
  color: var(--color-muted);
}

.lang-switcher a:hover {
  color: var(--color-accent);
  border-color: var(--color-accent);
}

main {
  padding: calc(var(--spacing) * 1.5) var(--spacing);
}

.page-header h1 {
  font-size: 1.875rem;
  margin: 0 0 0.5rem;
  line-height: 1.25;
  color: var(--color-accent);
}

.page-desc {
  color: var(--color-muted);
  font-size: 1.1rem;
  margin: 0 0 var(--spacing);
}

.page-content {
  margin-top: var(--spacing);
}

.page-list-items {
  list-style: none;
  padding: 0;
  margin: var(--spacing) 0 0;
}

.page-list-items li {
  border-bottom: 1px solid var(--color-border);
  padding: var(--spacing) 0;
}

.page-list-items li:first-child {
  border-top: 1px solid var(--color-border);
}

.page-list-items a {
  font-size: 1.1rem;
  font-weight: 600;
}

.page-list-items p {
  margin: 0.25rem 0 0;
  color: var(--color-muted);
}

.section-nav ul {
  list-style: none;
  padding: 0;
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
  margin: var(--spacing) 0 0;
}

.section-nav a {
  font-weight: 600;
}

img {
  max-width: 100%;
  height: auto;
  display: block;
  border-radius: 4px;
}

figure {
  margin: var(--spacing) 0;
}

figure figcaption {
  font-size: 0.875rem;
  color: var(--color-muted);
  margin-top: 0.25rem;
}

.img-center {
  margin-left: auto;
  margin-right: auto;
}

.img-left {
  float: left;
  margin-right: var(--spacing);
  margin-bottom: 0.5rem;
  max-width: 45%;
}

.img-right {
  float: right;
  margin-left: var(--spacing);
  margin-bottom: 0.5rem;
  max-width: 45%;
}

.page-content::after {
  content: "";
  display: table;
  clear: both;
}

.site-footer {
  background: var(--color-footer-bg);
  border-top: 1px solid var(--color-border);
  padding: var(--spacing) 0;
  margin-top: calc(var(--spacing) * 2);
  font-size: 0.875rem;
  color: var(--color-muted);
}

.site-footer .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.site-footer p {
  margin: 0;
}

.lang-nav {
  display: flex;
  gap: 0.75rem;
}

.lang-nav a {
  color: var(--color-muted);
  text-decoration: none;
}

.lang-nav a:hover {
  color: var(--color-accent);
}

@media (max-width: 600px) {
  .site-header .container {
    flex-direction: column;
    align-items: flex-start;
  }

  .lang-switcher {
    margin-left: 0;
  }

  .img-left,
  .img-right {
    float: none;
    max-width: 100%;
    margin: var(--spacing) 0;
  }
}