/* ===========================================================================
   tau.education — design tokens
   Single source for color, type and spacing. Values are final and come from
   IMPLEMENTATION.md §1. Change here to retune the whole site.
   =========================================================================== */

:root {
  /* --- Dark base (the site is charcoal-dominant) --- */
  --bg: #262626;              /* page + normal bands */
  --bg-alt: #242424;          /* alternating bands (tesis, problema, sobre tau) */
  --bg-sunken: #1F1F1F;       /* research band on Home; inputs */
  --bg-footer: #1A1A1A;
  --surface-code: #1B1B1B;    /* notebook body */
  --surface-code-bar: #212121;/* notebook title bar, figure panel */
  --surface-formula: #232323; /* formula box */
  --hover-row: rgba(217,217,217,.03);
  --card: #2B2B2B;            /* academy ficha hover */

  /* --- Light block (same grey bed as the logo) --- */
  --light: #D9D9D9;
  --light-card: #EDECEA;
  --on-light: #1C1C1C;
  --on-light-body: #3D3D3D;
  --on-light-meta: #5C5C5C;

  /* --- Text on dark --- */
  --fg-display: #F2F1EF;      /* H1 / H2 */
  --fg: #E6E5E3;              /* H3, active nav, strong text */
  --fg-body: #B9B7B3;         /* paragraphs */
  --fg-muted: #9C9A96;        /* secondary paragraphs, inactive nav */
  --fg-meta: #7A7874;         /* mono / meta */
  --fg-faint: #5C5C5C;        /* mono footnotes */

  /* --- Institutional accent: ONE colour, reserved for structure --- */
  --accent: #6BB0C7;
  --accent-hover: #9CCEDC;
  --accent-line: rgba(107,176,199,.40);
  --accent-border: rgba(107,176,199,.34);
  --accent-tint: rgba(107,176,199,.06);

  /* --- Hairlines: all derive from rgba(217,217,217,a) --- */
  --line-08: rgba(217,217,217,.08);
  --line-10: rgba(217,217,217,.10);
  --line-12: rgba(217,217,217,.12);  /* section + card-grid separators */
  --line-14: rgba(217,217,217,.14);  /* nav + notebook border */
  --line-16: rgba(217,217,217,.16);  /* card border */
  --line-20: rgba(217,217,217,.20);
  --line-22: rgba(217,217,217,.22);  /* input border */
  --line-25: rgba(217,217,217,.25);
  --line-28: rgba(217,217,217,.28);  /* secondary button border */
  --line-30: rgba(217,217,217,.30);

  /* --- Fonts --- */
  --font-wordmark: 'Anta', system-ui, sans-serif;          /* wordmark ONLY */
  --font-text: 'Didact Gothic', system-ui, sans-serif;     /* headings + body */
  --font-mono: 'IBM Plex Mono', ui-monospace, 'SF Mono', Menlo, monospace;

  /* --- Layout --- */
  --content-width: 1100px;
  --pad-x: 44px;
  --pad-x-mobile: 20px;
  --section-y: 104px;
  --section-y-mobile: 44px;
  --header-h: 74px;

  --radius-sm: 2px;   /* buttons, chips, inputs */
  --radius-nb: 3px;   /* notebook container */

  --ease: cubic-bezier(.2,0,0,1);
  --dur: 140ms;
}