/* ================================================================
   AI Stability Framework -- Site Stylesheet
   System-aware light/dark via prefers-color-scheme
   No JS. No framework. No theme dependency.
   ================================================================ */

/* --- Inter variable font (self-hosted, SIL OFL) --- */
@font-face {
  font-family: "Inter";
  font-style: normal;
  font-weight: 100 900;
  font-display: swap;
  src: url("/assets/fonts/Inter-Variable/web/InterVariable.woff2") format("woff2");
}

/* --- Light mode (default) --- */
:root {
  --color-bg:           #ffffff;
  --color-text:         #1a1a1a;
  --color-header-bg:    #f5f5f5;
  --color-header-border:#dddddd;
  --color-heading:      #111111;
  --color-rule:         #cccccc;
  --color-code-bg:      #f0f0f0;
  --color-muted:        #555555;
  --font-body:          "Inter", system-ui, -apple-system, sans-serif;
  --font-mono:          'Courier New', Courier, monospace;
}

/* --- Dark mode --- */
@media (prefers-color-scheme: dark) {
  :root {
    --color-bg:           #1c1c1c;
    --color-text:         #e6e6e6;
    --color-header-bg:    #242424;
    --color-header-border:#3a3a3a;
    --color-heading:      #f0f0f0;
    --color-rule:         #3a3a3a;
    --color-code-bg:      #2a2a2a;
    --color-muted:        #999999;
  }
}

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

html {
  background-color: var(--color-bg);
}

html, body {
  margin: 0;
  padding: 0;
}

body {
  background-color: var(--color-bg);
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: 1.0625rem;
  line-height: 1.75;
  letter-spacing: 0.020em;
}

/* --- Skip link --- */
.skip-link {
  position: absolute;
  top: -100%;
  left: 0;
  padding: 0.5rem 1rem;
  font-family: var(--font-body);
  font-size: 0.9rem;
  font-weight: 600;
  text-decoration: none;
  z-index: 1000;
}

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

/* --- Site header --- */
.site-header {
  background-color: var(--color-header-bg);
  border-bottom: 1px solid var(--color-header-border);
  padding: 0.75rem 2rem;
}

.site-brand {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  text-decoration: none;
  color: var(--color-heading);
}

.site-brand:hover {
  text-decoration: underline;
}

.site-logo {
  display: block;
  height: 2rem;
  width: auto;
}

.site-name {
  font-weight: 700;
  font-size: 1rem;
  line-height: 1.3;
}

/* --- Main content --- */
main {
  max-width: 780px;
  margin: 0 auto;
  padding: 2rem 1.5rem;
  background-color: var(--color-bg);
  color: var(--color-text);
}

/* --- Headings --- */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-body);
  color: var(--color-heading);
  line-height: 1.3;
  margin: 2rem 0 0.5rem 0;
}

h1 {
  font-size: 1.75rem;
  margin-top: 0;
}

h2 { font-size: 1.35rem; }
h3 { font-size: 1.1rem; }

/* --- Body text --- */
p {
  margin: 0 0 1rem 0;
  max-width: 72ch;
}

hr {
  border: none;
  border-top: 1px solid var(--color-rule);
  margin: 2rem 0;
}

/* --- Lists --- */
ul, ol {
  padding-left: 1.5rem;
  margin: 0 0 1rem 0;
  max-width: 72ch;
}

li {
  margin-bottom: 0.25rem;
}

/* --- Blockquote --- */
blockquote {
  margin: 1rem 0;
  padding-left: 1.25rem;
  border-left: 3px solid var(--color-rule);
  color: var(--color-muted);
}

/* --- Code --- */
code {
  font-family: var(--font-mono);
  font-size: 0.875em;
  background-color: var(--color-code-bg);
  padding: 0.1em 0.3em;
  border-radius: 3px;
}

pre {
  background-color: var(--color-code-bg);
  padding: 1rem;
  overflow-x: auto;
  border-radius: 4px;
  margin: 0 0 1rem 0;
}

pre code {
  background: none;
  padding: 0;
  font-size: 0.875rem;
}

/* --- Tables --- */
table {
  border-collapse: collapse;
  width: 100%;
  font-family: var(--font-body);
  font-size: 0.9rem;
  margin-bottom: 1rem;
}

th, td {
  border: 1px solid var(--color-rule);
  padding: 0.5rem 0.75rem;
  text-align: left;
}

th {
  background-color: var(--color-header-bg);
  font-weight: 600;
}

/* --- Strong --- */
strong {
  font-weight: 700;
}

/* --- Footnotes (kramdown) --- */
.footnotes {
  font-size: 0.9rem;
  margin-top: 2.5rem;
  padding-top: 1rem;
  border-top: 1px solid var(--color-rule);
  color: var(--color-muted);
}

.footnotes ol {
  margin: 0;
  padding-left: 1.25rem;
}

.footnotes li {
  margin-bottom: 0.4rem;
}

/* --- Chapter prev/next nav --- */
.chapter-nav {
  display: flex;
  flex-direction: row-reverse;
  justify-content: center;
  gap: 2rem;
  margin: 2rem 0 0.5rem 0;
}

/* --- TOC link (below chapter nav) --- */
.toc-link {
  text-align: center;
  margin-bottom: 2rem;
}

/* --- Footer --- */
footer {
  margin-top: 3rem;
  padding-top: 1rem;
  border-top: 1px solid var(--color-rule);
  font-family: var(--font-body);
  font-size: 0.85rem;
  color: var(--color-muted);
}

footer p {
  max-width: none;
  margin: 0;
}

/* --- Responsive --- */
@media (max-width: 600px) {
  .site-header {
    padding: 0.75rem 1rem;
  }

  main {
    padding: 1.5rem 1rem;
  }

  .chapter-nav {
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
  }
}