/* Light theme (default) */
:root, [data-theme="light"] {
  --text: #1a1a1a;
  --bg: #fdfdfd;
  --accent: #2563eb;
  --muted: #6b7280;
  --border: #e5e7eb;
  --code-bg: #f3f4f6;
  --toggle-bg: #e5e7eb;
  --toggle-hover: #d1d5db;
}

/* Dark theme */
[data-theme="dark"] {
  --text: #e5e7eb;
  --bg: #111827;
  --accent: #60a5fa;
  --muted: #9ca3af;
  --border: #374151;
  --code-bg: #1f2937;
  --toggle-bg: #374151;
  --toggle-hover: #4b5563;
}

/* System preference fallback (when no data-theme is set) */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) {
    --text: #e5e7eb;
    --bg: #111827;
    --accent: #60a5fa;
    --muted: #9ca3af;
    --border: #374151;
    --code-bg: #1f2937;
    --toggle-bg: #374151;
    --toggle-hover: #4b5563;
  }
}

* { margin: 0; padding: 0; box-sizing: border-box; }

body {
  font-family: system-ui, -apple-system, sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.7;
  width: 90%;
  max-width: 72rem;
  margin: 0 auto;
  padding: 2rem 0;
  transition: background 0.2s, color 0.2s;
}

/* Theme toggle */
.theme-toggle {
  position: fixed;
  top: 1rem;
  right: 1rem;
  display: flex;
  gap: 0.25rem;
  background: var(--toggle-bg);
  border-radius: 6px;
  padding: 0.2rem;
  z-index: 100;
}

.theme-toggle button {
  background: none;
  border: none;
  padding: 0.35rem 0.5rem;
  border-radius: 4px;
  cursor: pointer;
  font-size: 0.85rem;
  color: var(--muted);
  line-height: 1;
  transition: background 0.15s, color 0.15s;
}

.theme-toggle button:hover {
  background: var(--toggle-hover);
}

.theme-toggle button.active {
  background: var(--bg);
  color: var(--text);
  box-shadow: 0 1px 3px rgba(0,0,0,0.15);
}

/* Article nav — links to other formats */
.article-nav {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
  padding: 0.75rem 0;
  margin-bottom: 1.5rem;
  border-bottom: 1px solid var(--border);
  font-size: 0.9rem;
}

.article-nav a {
  color: var(--accent);
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
}

.article-nav a:hover { text-decoration: underline; }

/* Header */
header {
  margin-bottom: 1rem;
  padding-bottom: 1.5rem;
  border-bottom: 2px solid var(--border);
}

header .title {
  font-size: clamp(1.8rem, 4vw, 3rem);
  margin-bottom: 0.25rem;
}

header .author,
header .date {
  color: var(--muted);
  font-size: 1rem;
}

/* Headings */
h1 { font-size: clamp(1.6rem, 3.5vw, 2.4rem); margin: 2rem 0 0.75rem; }
h2 { font-size: clamp(1.2rem, 2.5vw, 1.6rem); margin: 2.5rem 0 0.75rem; border-bottom: 1px solid var(--border); padding-bottom: 0.3rem; }
h3 { font-size: clamp(1.05rem, 2vw, 1.25rem); margin: 1.5rem 0 0.5rem; }

p { margin: 0.75rem 0; font-size: clamp(0.95rem, 1.5vw, 1.1rem); }

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

ol, ul { padding-left: 1.5rem; margin: 0.75rem 0; }
li { margin: 0.3rem 0; font-size: clamp(0.95rem, 1.5vw, 1.1rem); }

/* Images — fully responsive */
img {
  max-width: 100%;
  height: auto;
  display: block;
  margin: 1.5rem auto;
}

figure {
  margin: 2rem 0;
  text-align: center;
}

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

figcaption {
  color: var(--muted);
  font-size: 0.85rem;
  margin-top: 0.5rem;
  font-style: italic;
}

/* SVG inline containers */
svg {
  max-width: 100%;
  height: auto;
}

/* Diagram container — responsive */
.diagram {
  width: 100%;
  overflow-x: auto;
  margin: 2rem 0;
  text-align: center;
}

.diagram svg {
  width: 100%;
  max-width: 100%;
  height: auto;
  min-width: 320px;
}

/* Code */
code {
  font-family: ui-monospace, "Cascadia Code", "Fira Code", monospace;
  font-size: 0.9em;
  background: var(--code-bg);
  padding: 0.15em 0.35em;
  border-radius: 3px;
}

pre {
  background: var(--code-bg);
  padding: 1.25rem;
  border-radius: 6px;
  overflow-x: auto;
  margin: 1.5rem 0;
  font-size: clamp(0.8rem, 1.2vw, 0.95rem);
}

pre code { background: none; padding: 0; }

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

strong { font-weight: 600; }

/* Responsive breakpoints */
@media (min-width: 1200px) {
  body { width: 85%; }
  figure img { max-width: 80%; }
}

@media (min-width: 768px) and (max-width: 1199px) {
  body { width: 90%; }
}

@media (max-width: 767px) {
  body { width: 100%; padding: 1rem; }
  header { margin-bottom: 1.5rem; padding-bottom: 1rem; }
  pre { padding: 0.75rem; font-size: 0.8rem; }
  .theme-toggle { top: 0.5rem; right: 0.5rem; }
}

/* Print */
@media print {
  body { width: 100%; max-width: none; padding: 0; }
  img { max-width: 100%; page-break-inside: avoid; }
  pre { white-space: pre-wrap; }
  .theme-toggle { display: none; }
}