/* Global design tokens */
:root {
  --font-main: 16px/1.6 system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Ubuntu, Inter, Arial, sans-serif;
  --radius-card: 16px;
  --radius-btn: 14px;
  --shadow-focus: 0 0 0 2px rgba(122,162,255,.6);
}

/* Themes */
body.theme-dark {
  --bg: #0b0b10;
  --fg: #e9ecf1;
  --muted: #a8b0bd;
  --card: #13131a;
  --acc: #7aa2ff;
  --bd: #1b1f2a;
}

body.theme-light {
  --bg: #ffffff;
  --fg: #1b1b1f;
  --muted: #555555;
  --card: #f6f6f8;
  --acc: #0056ff;
  --bd: #e2e2e6;
}

/* Base layout and typography */
*,
*::before,
*::after {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--fg);
  font: var(--font-main);
}

a {
  color: var(--acc);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

a:focus-visible,
button:focus-visible,
[role="button"]:focus-visible {
  outline: none;
  box-shadow: var(--shadow-focus);
}

img {
  max-width: 100%;
  height: auto;
}

/* Wrappers */
.wrap {
  max-width: 900px;
  margin: 0 auto;
  padding: 36px 20px;
}

.wrap--wide {
  max-width: 1080px;
  padding-inline: 24px;
}

/* Headings */
h1 {
  font-size: 32px;
  margin: 8px 0 10px;
  font-weight: 700;
  line-height: 1.3;
}

h2 {
  font-size: 22px;
  margin: 18px 0 8px;
  font-weight: 700;
}

h3 {
  font-size: 18px;
  margin: 14px 0 6px;
  font-weight: 600;
}

/* Header / navigation */
.header-nav,
header.site-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 20px 0;
  margin-bottom: 20px;
  border-bottom: 1px solid var(--bd);
}

.header-nav--no-border {
  border-bottom: none;
}

.back,
.nav-link {
  font-size: 14px;
  color: var(--muted);
}

.nav-link--primary {
  color: var(--acc);
}

@media (max-width: 480px) {
  .header-nav,
  header.site-header {
    flex-direction: column;
    align-items: flex-start;
    gap: 6px;
  }
}

/* Cards and layout blocks */
.card {
  background: var(--card);
  border: 1px solid var(--bd);
  border-radius: var(--radius-card);
  padding: 16px;
  margin: 16px 0;
}

.card--spacious {
  padding: 26px 28px;
}

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 14px;
  margin: 10px 0 34px;
}

.tag {
  display: inline-block;
  border-radius: 999px;
  border: 1px solid #243047;
  padding: 4px 10px;
  font-size: 12px;
  color: var(--muted);
  margin-top: 4px;
  letter-spacing: .05em;
  text-transform: uppercase;
}

.section-label {
  font-size: 13px;
  text-transform: uppercase;
  letter-spacing: .08em;
  color: var(--muted);
  margin-bottom: 4px;
}

.lead {
  color: var(--muted);
  font-size: 18px;
}

/* Buttons */
.btn,
.btn-top,
.cta-button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  padding: 14px 18px;
  border-radius: var(--radius-btn);
  border: 1px solid #243047;
  background: #0f1522;
  font-weight: 600;
  font-size: 15px;
  cursor: pointer;
}

.btn--secondary {
  background: transparent;
  border-color: var(--acc);
  color: var(--acc);
}

.btn--secondary:hover,
.cta-button:hover {
  background: var(--acc);
  color: #ffffff;
  text-decoration: none;
}

/* Light-theme CTA block */
.cta-block {
  margin-top: 50px;
  padding: 32px;
  border-radius: 18px;
  background: var(--card);
  border: 1px solid var(--bd);
}

.cta-title {
  margin: 0 0 12px;
  font-size: 24px;
  font-weight: 700;
}

.cta-text {
  margin: 0 0 24px;
  font-size: 16px;
  color: var(--muted);
  max-width: 700px;
}

/* TOC / related lists */
.toc {
  margin: 32px 0;
}

.toc-title {
  font-size: 22px;
  font-weight: 700;
  margin-bottom: 12px;
}

.toc-list {
  list-style: none;
  padding-left: 0;
  margin: 0;
}

.toc-list li {
  margin: 6px 0;
}

.related {
  margin-top: 50px;
}

.related ul {
  margin-left: 20px;
}

/* Footer */
footer {
  margin-top: 28px;
  padding-top: 20px;
  border-top: 1px solid var(--bd);
  color: var(--muted);
  font-size: 14px;
}

/* Screen reader only */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}