/* Lumen — Color
   Luminance-only palette. No chromatic accent; depth is signalled by
   graphite surfaces, hairline rims, and the single luminous horizon line. */
:root {
  /* Base surfaces — darkest to raised */
  --color-void: #1b1c22;        /* page background */
  --color-graphite: #0b151e;    /* deep base of gradients */
  --color-panel: #20222a;       /* default control / card fill */
  --color-panel-raised: #262932;/* hover / focus fill */
  --color-slate-rise: #47515c;  /* top of the surface radial */

  /* Lines & text */
  --color-hairline: #2f3441;    /* rim / divider */
  --color-foreground: #ffffff;  /* primary text */
  --color-muted: #a8aebb;       /* secondary text */
  --color-lumen: #cfd8e6;       /* the luminous highlight tone */

  /* Alpha tokens for hairlines and overlays */
  --alpha-hairline: rgba(255, 255, 255, 0.1);
  --alpha-hairline-strong: rgba(255, 255, 255, 0.16);
  --alpha-foreground-66: rgba(255, 255, 255, 0.66);
  --alpha-foreground-12: rgba(255, 255, 255, 0.12);
  --alpha-foreground-0: rgba(255, 255, 255, 0);

  /* Surface gradients — the system's material vocabulary */
  --surface-gradient: radial-gradient(
    ellipse at bottom,
    rgba(71, 81, 92, 1) 0%,
    rgba(11, 21, 30, 1) 45%
  );
  --surface-gradient-soft: radial-gradient(
    ellipse at bottom,
    rgba(71, 81, 92, 0.55) 0%,
    rgba(11, 21, 30, 0.95) 55%
  );
  --surface-panel-gradient: radial-gradient(
    ellipse at bottom,
    rgba(47, 52, 65, 0.6) 0%,
    rgba(20, 22, 30, 1) 65%
  );

  /* Horizon — the signature 70%-wide gradient highlight at the base */
  --horizon-line: linear-gradient(
    90deg,
    var(--alpha-foreground-0) 0%,
    var(--color-foreground) 50%,
    var(--alpha-foreground-0) 100%
  );
  --horizon-line-lumen: linear-gradient(
    90deg,
    var(--alpha-foreground-0) 0%,
    var(--color-lumen) 50%,
    var(--alpha-foreground-0) 100%
  );
}