@charset "UTF-8";

/* =========================================================
   Brand tokens: single source of color & type truth.
   Anchor: BITS "Signal Blue" #1668A8 (hex reference only;
   the hub keeps its own calm, prose-first personality).
   Cyan #06B6D4 is intentionally defined but unused: trace
   levels or absent, per the brand relationship.

   Every fg/bg pairing below is WCAG AA verified (≥4.5:1)
   in both light and dark mode.
   ========================================================= */

:root {
  /* ---- type ---- */
  --font-body: "Source Serif 4", "Iowan Old Style", "Palatino Linotype", Georgia, serif;
  --font-ui: "Muli", -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
  --font-mono: ui-monospace, "SF Mono", SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;

  --text-body: 1.1875rem;      /* 19px article prose */
  --text-small: 0.875rem;
  --leading-body: 1.7;
  --leading-heading: 1.3;
  --measure: 75ch;             /* comfortable prose measure */
  --measure-wide: 60rem;       /* breakout width: title, callouts, code, media */

  /* ---- brand anchors ---- */
  --signal-blue: #1668A8;
  --signal-blue-deep: #114E7F;
  --signal-blue-tint: #EAF2F8;
  --bits-cyan: #06B6D4;        /* trace use only; currently unused on purpose */

  /* ---- light mode (default) ---- */
  --color-surface: #FFFFFF;
  --color-surface-subtle: #F6F8FA;
  --color-border: #D9E2EA;

  --color-ink: #40474D;
  --color-ink-muted: #5C666E;
  --color-heading: #343A40;

  --color-link: var(--signal-blue);
  --color-link-hover: var(--signal-blue-deep);

  --color-primary: var(--signal-blue);
  --color-primary-deep: var(--signal-blue-deep);
  --color-primary-tint: var(--signal-blue-tint);
  --color-on-primary: #FFFFFF;

  --color-code-accent: #B2361C;    /* inline code */
  --color-code-ink: #565E66;       /* code block default ink */
  --color-code-bg: #F6F8FA;
  --color-code-border: #D9E2EA;

  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root {
    --color-surface: #14181D;
    --color-surface-subtle: #1C2127;
    --color-border: #2E3841;

    --color-ink: #D6DBE0;
    --color-ink-muted: #9AA5AE;
    --color-heading: #E4E8EC;

    --color-link: #7FB8E6;
    --color-link-hover: #A6CDEF;

    --color-primary: #1668A8;
    --color-primary-deep: #114E7F;
    --color-primary-tint: #1B2937;
    --color-on-primary: #FFFFFF;

    --color-code-accent: #F0906E;
    /* code blocks use the github-dark Chroma theme (see css/syntax.css).
       These match its surface so the pre chrome (border, base text) agrees. */
    --color-code-ink: #E6EDF3;
    --color-code-bg: #0D1117;
    --color-code-border: #30363D;

    color-scheme: dark;
  }
}