:root {
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --font-serif: Georgia, "Times New Roman", serif;

  --color-bg: #ffffff;
  --color-bg-alt: #f6f8fa;
  --color-surface: #ffffff;
  --color-border: #e2e6ea;
  --color-text: #1a2433;
  --color-text-muted: #55606e;
  --color-primary: #0b3d62;
  --color-primary-dark: #082b46;
  --color-accent: #0f8f7e;
  --color-accent-dark: #0b6c5f;
  --color-warning-bg: #fff6e5;
  --color-warning-border: #f0c975;
  --color-link: #0b5d8f;

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --shadow-sm: 0 1px 2px rgba(16, 24, 40, 0.06);
  --shadow-md: 0 4px 12px rgba(16, 24, 40, 0.08);
  --max-width: 1120px;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --color-bg: #0e141b;
    --color-bg-alt: #141c25;
    --color-surface: #161f29;
    --color-border: #263241;
    --color-text: #e7edf3;
    --color-text-muted: #a7b3c0;
    --color-primary: #5fa8d3;
    --color-primary-dark: #3f87b3;
    --color-accent: #35c2a8;
    --color-accent-dark: #28a890;
    --color-warning-bg: #2a2410;
    --color-warning-border: #6b551b;
    --color-link: #7cc1ef;
  }
}

:root[data-theme="dark"] {
  --color-bg: #0e141b;
  --color-bg-alt: #141c25;
  --color-surface: #161f29;
  --color-border: #263241;
  --color-text: #e7edf3;
  --color-text-muted: #a7b3c0;
  --color-primary: #5fa8d3;
  --color-primary-dark: #3f87b3;
  --color-accent: #35c2a8;
  --color-accent-dark: #28a890;
  --color-warning-bg: #2a2410;
  --color-warning-border: #6b551b;
  --color-link: #7cc1ef;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--color-bg);
  color: var(--color-text);
  font-family: var(--font-sans);
  font-size: 17px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

img, svg, video { max-width: 100%; height: auto; display: block; }

a { color: var(--color-link); }
a:hover { text-decoration-thickness: 2px; }

h1, h2, h3, h4 {
  font-family: var(--font-sans);
  line-height: 1.25;
  font-weight: 700;
  color: var(--color-text);
}
h1 { font-size: clamp(2rem, 4vw, 2.75rem); }
h2 { font-size: clamp(1.5rem, 3vw, 2rem); margin-top: 2.5em; }
h3 { font-size: clamp(1.2rem, 2vw, 1.4rem); margin-top: 1.75em; }

p { margin: 0 0 1.2em; }

.container {
  max-width: var(--max-width);
  margin-inline: auto;
  padding-inline: 1.25rem;
}

.prose p, .prose li { color: var(--color-text); }
.prose { max-width: 72ch; }
.prose ul, .prose ol { padding-left: 1.4em; }
.prose li { margin-bottom: 0.5em; }
.prose table { width: 100%; border-collapse: collapse; margin: 1.5em 0; }
.prose th, .prose td {
  border: 1px solid var(--color-border);
  padding: 0.6em 0.8em;
  text-align: left;
  font-size: 0.95em;
}
.prose th { background: var(--color-bg-alt); }

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5em;
  padding: 0.75em 1.4em;
  border-radius: var(--radius-md);
  font-weight: 600;
  text-decoration: none;
  min-height: 48px;
  cursor: pointer;
  border: 1px solid transparent;
}
.btn-primary {
  background: var(--color-accent);
  color: #fff;
}
.btn-primary:hover { background: var(--color-accent-dark); }
.btn-outline {
  background: transparent;
  border-color: var(--color-border);
  color: var(--color-text);
}

.card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
}

.callout {
  background: var(--color-warning-bg);
  border: 1px solid var(--color-warning-border);
  border-radius: var(--radius-md);
  padding: 1.1em 1.3em;
  margin: 1.75em 0;
  font-size: 0.97em;
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--color-primary);
  color: #fff;
  padding: 0.75em 1.25em;
  z-index: 1000;
  border-radius: 0 0 var(--radius-sm) 0;
}
.skip-link:focus { left: 0; }

.visually-hidden {
  position: absolute;
  width: 1px; height: 1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
}

@media (max-width: 640px) {
  body { font-size: 16px; }
}