/* ── Reset ── */
*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }
button, input, select, textarea { font: inherit; }
html { scroll-behavior: smooth; }
html, body { width: 100%; height: 100%; }

/* ── Color tokens ── */
:root {
  --bg: #f5f5f3;
  --text: #18181b;
  --text-secondary: #71717a;
  --accent: #4f46e5;
  --rule: #e4e4e7;
  --mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
}

@media (prefers-color-scheme: dark) {
  :root:not(.light) {
    --bg: #000;
    --text: #e4e4e7;
    --text-secondary: #a1a1aa;
    --accent: #818cf8;
    --rule: #27272a;
  }
}

:root.dark, :root.dmt {
  --bg: #000;
  --text: #e4e4e7;
  --text-secondary: #a1a1aa;
  --accent: #818cf8;
  --rule: #27272a;
}

:root.light {
  --bg: #f5f5f3;
  --text: #18181b;
  --text-secondary: #71717a;
  --accent: #4f46e5;
  --rule: #e4e4e7;
}

/* ── Body base ── */
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  transition: background-color 0.4s ease, color 0.4s ease;
}

/* ── Page container ── */
.page {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 clamp(32px, 6vw, 80px);
}

.page--narrow {
  max-width: 800px;
}

/* ── Dividers ── */
hr {
  border: none;
  border-top: 1px solid var(--rule);
  margin: 0;
  transition: border-color 0.4s ease;
}

/* ── Sections ── */
.section {
  padding: clamp(20px, 3vw, 36px) 0;
}

.section-label {
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--text-secondary);
  margin-bottom: clamp(12px, 1.5vw, 20px);
  transition: color 0.4s ease;
}

/* ── Sub-page topbar ── */
.sub-topbar {
  display: flex;
  align-items: center;
  gap: 0.6em;
  padding: clamp(16px, 2vw, 24px) 0;
  font-size: 0.8rem;
  font-weight: 500;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.sub-topbar a {
  color: var(--text);
  text-decoration: none;
  transition: color 0.2s ease;
}

.sub-topbar a:hover {
  color: var(--accent);
}

.sub-topbar .home-link strong {
  font-weight: 900;
}

.sub-topbar .sep {
  color: var(--text-secondary);
}

.sub-topbar .crumb {
  color: var(--text-secondary);
  font-weight: 400;
}

/* ── Content typography ── */
h1, h2, h3 { line-height: 1.2; }

h1 {
  font-size: clamp(1.8rem, 3.5vw, 2.6rem);
  font-weight: 800;
  letter-spacing: -0.02em;
  text-transform: uppercase;
  margin-bottom: clamp(12px, 1.5vw, 18px);
}

h2 {
  font-size: clamp(1.2rem, 2vw, 1.6rem);
  font-weight: 700;
  letter-spacing: -0.01em;
  margin-bottom: 12px;
}

h3 {
  font-size: 1.15rem;
  font-weight: 600;
  margin-bottom: 8px;
}

.content h3:not(:first-child) {
  margin-top: 1.75rem;
}

.content > section > p,
.content > section > ul > li {
  max-width: 65ch;
}

.content p {
  color: var(--text-secondary);
  margin-bottom: 1em;
  transition: color 0.4s ease;
}

.content p:last-child {
  margin-bottom: 0;
}

.content ul {
  padding-left: 1.5em;
  margin-bottom: 1em;
  color: var(--text-secondary);
  transition: color 0.4s ease;
}

.content li {
  margin-bottom: 0.4em;
}

.content code {
  font-size: 0.9em;
  background: var(--rule);
  padding: 0.15em 0.4em;
  border-radius: 3px;
  transition: background-color 0.4s ease;
}

.content em {
  color: var(--text-secondary);
}

/* ── Links ── */
a {
  color: var(--accent);
  text-decoration: none;
  transition: color 0.2s ease;
}

a:hover {
  color: var(--text);
}

a:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
  border-radius: 2px;
}

/* ── Feature list (checkmarks) ── */
.feature-list {
  list-style: none;
  padding: 0;
}

.feature-list li {
  padding: 2px 0;
}

.feature-list li::before {
  content: "\2713\00a0\00a0";
  color: var(--accent);
  font-weight: bold;
}

/* ── Footer ── */
.site-footer {
  padding: clamp(20px, 3vw, 36px) 0 clamp(16px, 2vw, 28px);
}

.footer-inner {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  flex-wrap: wrap;
  gap: 12px;
}

.footer-location,
.footer-copy {
  font-size: 0.72rem;
  font-weight: 500;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--text-secondary);
  transition: color 0.4s ease;
}

.footer-copy strong {
  font-weight: 800;
}

/* ── Mode switcher ── */
.mode-switcher {
  position: fixed;
  bottom: 1.5rem;
  right: 1.5rem;
  z-index: 10;
  display: flex;
  border: 1px solid var(--text);
  border-radius: 6px;
  overflow: hidden;
  opacity: 0.35;
  transition: opacity 0.2s, border-color 0.4s;
}

.mode-switcher:hover {
  opacity: 1;
}

.mode-switcher button {
  background: none;
  border: none;
  color: var(--text);
  font-size: 0.65rem;
  font-weight: 500;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  padding: 0.5em 1em;
  cursor: pointer;
  transition: background 0.4s, color 0.4s;
  opacity: 0.5;
}

.mode-switcher button + button {
  border-left: 1px solid var(--text);
}

.mode-switcher button.active {
  background: var(--text);
  color: var(--bg);
  opacity: 1;
}

.mode-switcher button:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: -2px;
}

/* ── Reduced motion ── */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

/* ── Mobile ── */
@media (max-width: 600px) {
  .footer-inner {
    flex-direction: column;
    gap: 6px;
  }
}