:root {
  /* Brand */
  --brand-ink: #101a2b;
  --brand-prussian: #1b4c7e;
  --brand-verdigris: #3e7c6a;

  --color-bg: #fff;
  --color-text: #101a2b;
  --color-text-muted: #4f5a6b;
  --color-link: #1b4c7e;
  --color-link-visited: #4a3f7a;
  --color-border: #d9dee6;
  --color-code-bg: #f3f5f8;
  --color-header-bg: #fafbfc;
  --color-accent: #3e7c6a;
  --color-button-bg: #1b4c7e;
  --color-button-text: #ffffff;
  --max-width: 42rem;

  /* Ambient signal fabric (decorative canvas). Low alpha keeps text contrast intact. */
  --signal-path-a: rgba(27, 76, 126, 0.2);
  --signal-path-b: rgba(62, 124, 106, 0.2);
  --signal-path-c: rgba(28, 122, 150, 0.18);
  --signal-node: rgba(27, 76, 126, 0.34);
  --signal-packet: rgba(27, 118, 156, 0.88);
  --signal-packet-glow: rgba(27, 118, 156, 0.2);
  --signal-marker: rgba(62, 124, 106, 0.9);
  --signal-marker-idle: rgba(62, 124, 106, 0.4);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --color-bg: #0c121c;
    --color-text: #dfe5ee;
    --color-text-muted: #9aa6b8;
    --color-link: #7fb5e8;
    --color-link-visited: #b8a4e6;
    --color-border: #263244;
    --color-code-bg: #141c29;
    --color-header-bg: #0a0f17;
    --color-accent: #6fb3a0;
    --color-button-bg: #7fb5e8;
    --color-button-text: #0c121c;

    --signal-path-a: rgba(122, 170, 220, 0.2);
    --signal-path-b: rgba(111, 179, 160, 0.2);
    --signal-path-c: rgba(96, 184, 208, 0.18);
    --signal-node: rgba(122, 170, 220, 0.36);
    --signal-packet: rgba(126, 212, 232, 0.9);
    --signal-packet-glow: rgba(126, 212, 232, 0.2);
    --signal-marker: rgba(111, 179, 160, 0.95);
    --signal-marker-idle: rgba(111, 179, 160, 0.42);
  }
}

/* Explicit user choice from the theme control wins over the OS preference. */
:root[data-theme="dark"] {
    --color-bg: #0c121c;
    --color-text: #dfe5ee;
    --color-text-muted: #9aa6b8;
    --color-link: #7fb5e8;
    --color-link-visited: #b8a4e6;
    --color-border: #263244;
    --color-code-bg: #141c29;
    --color-header-bg: #0a0f17;
    --color-accent: #6fb3a0;
    --color-button-bg: #7fb5e8;
    --color-button-text: #0c121c;

    --signal-path-a: rgba(122, 170, 220, 0.2);
    --signal-path-b: rgba(111, 179, 160, 0.2);
    --signal-path-c: rgba(96, 184, 208, 0.18);
    --signal-node: rgba(122, 170, 220, 0.36);
    --signal-packet: rgba(126, 212, 232, 0.9);
    --signal-packet-glow: rgba(126, 212, 232, 0.2);
    --signal-marker: rgba(111, 179, 160, 0.95);
    --signal-marker-idle: rgba(111, 179, 160, 0.42);
}

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

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen,
    Ubuntu, Cantarell, "Helvetica Neue", Arial, sans-serif;
  font-size: 1rem;
  line-height: 1.6;
  color: var(--color-text);
  background-color: var(--color-bg);
}

a {
  color: var(--color-link);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 2px;
}

a:visited {
  color: var(--color-link-visited);
}

a:hover {
  text-decoration-thickness: 2px;
}

header {
  border-bottom: 1px solid var(--color-border);
  background-color: var(--color-header-bg);
}

header nav {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 1rem;
  display: flex;
  align-items: center;
  gap: 1.5rem;
  flex-wrap: wrap;
}

.site-name {
  font-weight: 700;
  font-size: 1.1rem;
  text-decoration: none;
  color: var(--color-text);
  letter-spacing: 0.05em;
  display: inline-flex;
  align-items: center;
  gap: 0.5em;
}

.site-name svg {
  width: 1.6em;
  height: 1.6em;
  color: var(--color-accent);
  flex: none;
}

header nav ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  gap: 1rem;
}

.nav-tools {
  margin-left: auto;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

@media (max-width: 640px) {
  header nav {
    gap: 0.75rem 1.25rem;
  }

  .nav-tools {
    order: 2;
  }

  .nav-links {
    order: 3;
    width: 100%;
  }
}

.lang-switch,
.theme-toggle {
  font: inherit;
  font-size: 0.85rem;
  line-height: 1.2;
  color: var(--color-text);
  background: none;
  border: 1px solid var(--color-border);
  border-radius: 3px;
  padding: 0.3em 0.6em;
  text-decoration: none;
}

.lang-switch {
  font-weight: 600;
  letter-spacing: 0.06em;
}

.lang-switch:visited {
  color: var(--color-text);
}

.lang-switch:hover,
.theme-toggle:hover {
  border-color: var(--color-accent);
  text-decoration: none;
}

.theme-toggle {
  cursor: pointer;
}

.theme-toggle span {
  display: inline-flex;
  align-items: center;
  gap: 0.4em;
}

.theme-toggle span[hidden] {
  display: none;
}

.theme-toggle svg {
  width: 0.95em;
  height: 0.95em;
}

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

.skip-link {
  position: absolute;
  left: 1rem;
  top: -3rem;
  z-index: 2;
  background: var(--color-bg);
  color: var(--color-text);
  padding: 0.5rem 0.75rem;
  border: 1px solid var(--color-accent);
}

.skip-link:focus {
  top: 1rem;
}

.lang-hint {
  position: relative;
  z-index: 1;
  border-bottom: 1px solid var(--color-border);
  background: var(--color-code-bg);
  font-size: 0.9rem;
}

.lang-hint p {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0.5rem 3rem 0.5rem 1rem;
}

.lang-hint button {
  position: absolute;
  right: max(1rem, calc(50% - var(--max-width) / 2 + 1rem));
  top: 50%;
  transform: translateY(-50%);
  font: inherit;
  font-size: 1.2rem;
  line-height: 1;
  background: none;
  border: none;
  color: var(--color-text-muted);
  cursor: pointer;
  padding: 0.2rem 0.4rem;
}

main {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 2rem 1rem;
}

.hero {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 2rem;
  align-items: center;
  margin: 0.5rem 0 1.25rem;
}

.hero h1 {
  font-size: 2rem;
  line-height: 1.2;
  margin: 0.25rem 0 0.75rem;
  text-wrap: balance;
}

.eyebrow {
  font-size: 0.78rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-accent);
  margin: 0;
}

.lede {
  font-size: 1.1rem;
  color: var(--color-text-muted);
}

.actions {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.75rem 1.25rem;
}

.button,
.button:visited {
  display: inline-block;
  background: var(--color-button-bg);
  color: var(--color-button-text);
  font-weight: 600;
  text-decoration: none;
  padding: 0.55em 1.1em;
  border-radius: 3px;
}

.button:hover {
  text-decoration: underline;
}

.portrait {
  margin: 0;
  text-align: center;
}

.portrait img {
  display: block;
  width: 168px;
  height: 168px;
  border-radius: 50%;
  margin: 0 auto;
  box-shadow: 0 0 0 3px var(--color-bg), 0 0 0 4px var(--color-accent);
}

.portrait figcaption {
  font-size: 0.8rem;
  color: var(--color-text-muted);
  margin-top: 0.6rem;
}

.proof {
  list-style: none;
  padding: 0;
  margin: 0 0 2rem;
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem 1.5rem;
  font-size: 0.85rem;
  color: var(--color-text-muted);
}

.proof li {
  display: flex;
  align-items: center;
  gap: 0.5em;
  margin: 0;
}

.proof li::before {
  content: "";
  width: 0.4em;
  height: 0.4em;
  border: 1px solid var(--color-accent);
  transform: rotate(45deg);
  flex: none;
}

.signature {
  color: var(--color-text-muted);
  font-style: italic;
}

@media (max-width: 640px) {
  .hero {
    grid-template-columns: 1fr;
    gap: 1.25rem;
  }

  .portrait {
    order: -1;
    text-align: left;
  }

  .portrait img {
    width: 120px;
    height: 120px;
    margin: 0;
  }

  .hero h1 {
    font-size: 1.7rem;
  }
}

/* Content sits above the decorative canvas. */
header,
main,
footer {
  position: relative;
  z-index: 1;
}

/* Ambient signal fabric: fixed, transparent, decorative, never interactive. */
.signal-field {
  position: fixed;
  inset: 0;
  width: 100%;
  height: 100%;
  z-index: 0;
  pointer-events: none;
  user-select: none;
  opacity: 0;
  transition: opacity 1.4s ease;
}

.signal-field.is-ready {
  opacity: 1;
}

@media (prefers-reduced-motion: reduce) {
  .signal-field {
    transition: none;
  }
}

@media print {
  .signal-field {
    display: none;
  }
}

h1, h2, h3, h4 {
  line-height: 1.3;
  margin-top: 2rem;
  margin-bottom: 0.5rem;
}

h1 { font-size: 1.8rem; }
h2 { font-size: 1.4rem; }
h3 { font-size: 1.15rem; }

p { margin: 0 0 1rem; }

ul, ol {
  padding-left: 1.5rem;
  margin: 0 0 1rem;
}

li { margin-bottom: 0.25rem; }

code {
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
  font-size: 0.9em;
  background-color: var(--color-code-bg);
  padding: 0.15em 0.3em;
  border-radius: 3px;
}

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

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

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

blockquote {
  margin: 0 0 1rem;
  padding: 0.5rem 1rem;
  border-left: 3px solid var(--color-accent);
  color: var(--color-text-muted);
}

footer {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 2rem 1rem;
  border-top: 1px solid var(--color-border);
  color: var(--color-text-muted);
  font-size: 0.85rem;
}

.post-header {
  margin-bottom: 2rem;
}

.post-header h1 {
  margin-top: 0;
  margin-bottom: 0.25rem;
}

.post-header time {
  color: var(--color-text-muted);
  font-size: 0.9rem;
}

.tags {
  list-style: none;
  padding: 0;
  display: flex;
  gap: 0.5rem;
  margin: 0.5rem 0 0;
}

.tags li {
  font-size: 0.8rem;
  color: var(--color-text-muted);
  border: 1px solid var(--color-border);
  padding: 0.1em 0.5em;
  border-radius: 3px;
}

/* Diagrams are pre-rendered from diagrams/*.mmd with a light palette, so they
   sit on their own light card in both themes. */
.post-body img[src^="/img/diagrams/"] {
  display: block;
  box-sizing: border-box;
  max-width: 100%;
  height: auto;
  margin: 1.5rem auto;
  padding: 0.75rem;
  background: #fff;
  border: 1px solid var(--color-border);
  border-radius: 6px;
}

.post-footer {
  margin-top: 3rem;
}

.post-footer .license {
  font-size: 0.85rem;
  color: var(--color-text-muted);
}

.cta {
  margin: 1.5rem 0;
  padding: 1rem;
  border: 1px solid var(--color-border);
  border-radius: 4px;
}

.cta h2 {
  font-size: 1.1rem;
  margin-top: 0;
}