Rework the CRT raster, glow and flicker effects

The three effects had drifted apart from each other and from the token
system. Consolidate them behind --crt-* tokens and fix what was broken.

- The animated text-shadow silently overrode the static one, so
  reduce-motion users saw a 5px white glow and everyone else a 3px
  currentColor glow. Both now come from one declaration, with the
  aberration offset factored out into --crt-shift.
- Step the aberration instead of tweening it. text-shadow is not
  compositable and this one inherits to every glyph, so the smooth
  version repainted the whole document at refresh rate.
- The flicker was invisible: a near-black tint at an effective alpha of
  0.008-0.096 over a black background, a peak lift of under 2/255.
  Retint with the accent at ~3%.
- Anchor the vignette to the viewport. It was sized to body's box, which
  is document-height, so on long pages the bloom sat off-screen.
- Pin the overlays with position: fixed rather than painting
  document-sized layers, and give the grille hard stops so it is three
  stripes rather than a smooth R->G->B ramp.
- Scale the raster pitch down at >=2dppx, where a 2px scanline is 4
  device px and resamples into moire at fractional DPR.
- Raise --color-mg to oklch(0.62): at 0.5 it was 3.5:1 on the
  background and 1.7:1 over the vignette centre. Halve the vignette
  alpha via its own token, keeping --color-accent-transparent at 50%
  for ProjectCard's glow.

Collapses the two keyframe blocks from 193 lines to 40.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

public/style.css

@@ -2,6 +2,20 @@
 @import "reset.css" layer(reset);
 @import "theme.css" layer(theme);
 
+/* The chromatic-aberration offset, as a 0..1 multiplier of
+   --crt-aberration-max. Registering it gives it a typed initial value, so the
+   calc() in body's text-shadow stays valid when the animation is not running.
+   Note the var(--crt-shift, 0) fallbacks at the use sites: without one, an
+   unresolved --crt-shift makes the calc() invalid at computed-value time,
+   which drops the *whole* text-shadow — glow included — not just the smear.
+   The animation itself does not depend on this rule, because step-end never
+   interpolates; it only ever substitutes a literal keyframe value. */
+@property --crt-shift {
+  syntax: "<number>";
+  inherits: true;
+  initial-value: 0;
+}
+
 @font-face {
   font-family: "unscii16";
   src:
@@ -45,13 +59,37 @@
   :root {
     /* Color */
     --color-fg: oklch(1 0 0);
-    --color-mg: oklch(0.5 0 0);
+    /* 0.62, not 0.5: at 0.5 this was 3.5:1 on the background, under AA, and
+       1.7:1 against the centre of the CRT vignette. 0.62 gives 5.8:1 / 4.4:1. */
+    --color-mg: oklch(0.62 0 0);
     --color-bg: oklch(0 0 0);
     --color-accent: oklch(0.6 0.18 142.5);
     --color-accent-bright: oklch(0.8 0.18 142.5);
     --color-glow: oklch(0.8328 0 0);
     --color-accent-transparent: oklch(0.6 0.18 142.5 / 50%);
 
+    /* CRT
+       The raster (scanline + aperture grille) and the phosphor (vignette,
+       glow, chromatic aberration). Every value the effect uses lives here so
+       the whole look can be retuned without touching the keyframes. */
+    --crt-scanline-pitch: 2px;
+    --crt-grille-pitch: 3px;
+    --crt-scanline-color: rgb(0 0 0 / 0.25);
+    --crt-grille-r: rgb(255 0 0 / 0.06);
+    --crt-grille-g: rgb(0 255 0 / 0.02);
+    --crt-grille-b: rgb(0 0 255 / 0.06);
+    /* Deliberately not --color-accent-transparent, which ProjectCard uses for
+       its box-shadow glow and wants at 50%. As a full-screen wash behind text,
+       50% costs too much contrast; 25% keeps --color-mg above 4.5:1. */
+    --crt-vignette-core: oklch(0.6 0.18 142.5 / 25%);
+    --crt-vignette-edge: var(--color-bg);
+    --crt-shadow-cool: rgb(0 30 255 / 0.5);
+    --crt-shadow-warm: rgb(255 0 80 / 0.3);
+    --crt-glow-blur: 3px;
+    /* In em so the smear scales with the fluid root font-size. */
+    --crt-aberration-max: 0.15em;
+    --crt-flicker-base: 0.03;
+
     /* Spacing */
     --gutter-large: clamp(3ch, 2.5vmax, 3.75ch);
     --stack-large: clamp(1.25ex, 2.5vmax, 1.75ex);
@@ -112,6 +150,16 @@
     }
   }
 
+  /* The raster is specified in CSS px, so on a 2dppx panel a 2px scanline is
+     4 device px — coarse, and on fractional DPR it resamples into moire.
+     Tightening the pitch keeps the apparent scale roughly constant. */
+  @media (min-resolution: 2dppx) {
+    :root {
+      --crt-scanline-pitch: 1.5px;
+      --crt-grille-pitch: 2.25px;
+    }
+  }
+
   @media (prefers-color-scheme: light) {
   }
 

public/theme.css

@@ -39,12 +39,21 @@ html {
   width: 100%;
   height: 100%;
 }
+/* The aberration is a discrete jitter, so it is stepped rather than
+   interpolated: step-end repaints 21 times per cycle instead of once per
+   frame. text-shadow is not compositable, and this one inherits to every
+   glyph on the page, so a smooth tween would repaint the whole document at
+   refresh rate. Stepping also reads more like chroma noise than a ramp does. */
 body {
-  animation: textShadow 1.6s infinite;
+  animation: crt-aberration 1.6s step-end infinite;
+  /* Anchors the vignette to the viewport. Without it the gradient is sized to
+     body's box, which is document-height, so on a long page its centre sits
+     at the middle of the document and the bloom is off-screen at scroll-top. */
+  background-attachment: fixed;
   background-color: var(--color-bg);
   background-image: radial-gradient(
-    var(--color-accent-transparent),
+    var(--crt-vignette-core),
-    black 120%
+    var(--crt-vignette-edge) 120%
   );
   color: var(--color-fg);
   column-gap: var(--gutter-large);
@@ -58,46 +67,56 @@ body {
   position: absolute;
   right: 0;
   row-gap: var(--stack-large);
-  text-shadow: 0 0 5px var(--color-glow);
+  /* Single source of truth for the glow: when the animation is off,
+     --crt-shift is 0 and this is exactly the static glow. Previously the
+     animation overrode a separate `0 0 5px var(--color-glow)` rule, so
+     reduce-motion users saw a 5px white glow and everyone else a 3px
+     currentColor one — two looks nobody had chosen. */
+  text-shadow:
+    calc(var(--crt-shift, 0) * var(--crt-aberration-max)) 0 1px
+      var(--crt-shadow-cool),
+    calc(var(--crt-shift, 0) * var(--crt-aberration-max) * -1) 0 1px
+      var(--crt-shadow-warm),
+    0 0 var(--crt-glow-blur) var(--color-glow);
   top: 0;
 }
+/* Fixed rather than absolute: these used to be document-sized layers that
+   relied on background-attachment to keep the pattern still. Pinning them to
+   the viewport gets the same effect while bounding the painted layer, and it
+   covers the screen regardless of how tall the content is. */
+body::before,
 body::after {
-  content: " ";
+  content: "";
-  display: block;
+  inset: 0;
-  position: absolute;
-  top: 0;
-  left: 0;
-  bottom: 0;
-  right: 0;
-  background: rgba(18, 16, 16, 0.1);
-  background-attachment: fixed;
-  opacity: 0;
-  z-index: 2;
   pointer-events: none;
-  animation: flicker 15s infinite;
+  position: fixed;
+  z-index: 2;
 }
+/* Scanlines and aperture grille. repeating-linear-gradient with hard stops
+   replaces background-size tiling: the grille used to be a smooth R->G->B
+   ramp across 3px, where a real grille is three discrete stripes. */
 body::before {
-  content: " ";
+  background-image:
-  display: block;
+    repeating-linear-gradient(
-  position: absolute;
+      transparent 0 calc(var(--crt-scanline-pitch) / 2),
-  top: 0;
+      var(--crt-scanline-color) 0 var(--crt-scanline-pitch)
-  left: 0;
+    ),
-  bottom: 0;
+    repeating-linear-gradient(
-  right: 0;
-  background:
-    linear-gradient(rgba(18, 16, 16, 0) 50%, rgba(0, 0, 0, 0.25) 50%),
-    linear-gradient(
       90deg,
-      rgba(255, 0, 0, 0.06),
+      var(--crt-grille-r) 0 calc(var(--crt-grille-pitch) / 3),
-      rgba(0, 255, 0, 0.02),
+      var(--crt-grille-g) 0 calc(var(--crt-grille-pitch) / 3 * 2),
-      rgba(0, 0, 255, 0.06)
+      var(--crt-grille-b) 0 var(--crt-grille-pitch)
     );
-  z-index: 2;
+}
-  background-size:
+/* Phosphor flicker. The old version tinted with rgba(18, 16, 16, 0.1) at
-    100% 2px,
+   0.08-0.96 opacity: an effective alpha of 0.008-0.096 of a colour ~7%
-    3px 100%;
+   lighter than the background, i.e. a peak lift of under 2/255. It was
-  background-attachment: fixed;
+   invisible. Tinting with the accent at ~3% is small enough to cost no
-  pointer-events: none;
+   measurable contrast and large enough to actually see. */
+body::after {
+  animation: crt-flicker 3s step-end infinite;
+  background: var(--color-accent);
+  opacity: var(--crt-flicker-base);
 }
 :root[data-reduce-motion="on"] body,
 :root[data-reduce-motion="on"] body::after {
@@ -132,197 +151,122 @@ body::before {
     animation: none;
   }
 }
-@keyframes flicker {
+@keyframes crt-flicker {
   0% {
-    opacity: 0.27861;
+    opacity: 0.03;
   }
-  5% {
+  7% {
-    opacity: 0.34769;
+    opacity: 0.024;
   }
-  10% {
+  13% {
-    opacity: 0.23604;
+    opacity: 0.041;
   }
-  15% {
+  19% {
-    opacity: 0.90626;
+    opacity: 0.028;
   }
-  20% {
+  26% {
-    opacity: 0.18128;
+    opacity: 0.019;
   }
-  25% {
+  31% {
-    opacity: 0.83891;
+    opacity: 0.036;
   }
-  30% {
+  38% {
-    opacity: 0.65583;
+    opacity: 0.026;
   }
-  35% {
+  44% {
-    opacity: 0.67807;
+    opacity: 0.048;
   }
-  40% {
+  51% {
-    opacity: 0.26559;
+    opacity: 0.022;
   }
-  45% {
+  58% {
-    opacity: 0.84693;
+    opacity: 0.033;
   }
-  50% {
+  63% {
-    opacity: 0.96019;
+    opacity: 0.017;
-  }
-  55% {
-    opacity: 0.08594;
-  }
-  60% {
-    opacity: 0.20313;
-  }
-  65% {
-    opacity: 0.71988;
   }
   70% {
-    opacity: 0.53455;
+    opacity: 0.039;
   }
-  75% {
+  77% {
-    opacity: 0.37288;
+    opacity: 0.027;
   }
-  80% {
+  83% {
-    opacity: 0.71428;
+    opacity: 0.044;
   }
-  85% {
+  91% {
-    opacity: 0.70419;
+    opacity: 0.021;
-  }
-  90% {
-    opacity: 0.7003;
-  }
-  95% {
-    opacity: 0.36108;
   }
   100% {
-    opacity: 0.24387;
+    opacity: 0.03;
   }
 }
-@keyframes textShadow {
+/* Normalised from the original per-keyframe pixel offsets, divided by their
+   max (3.8969px), so the rhythm is unchanged but the amplitude is now set in
+   one place by --crt-aberration-max. */
+@keyframes crt-aberration {
   0% {
-    text-shadow:
+    --crt-shift: 0.113;
-      0.4389924193300864px 0 1px rgba(0, 30, 255, 0.5),
-      -0.4389924193300864px 0 1px rgba(255, 0, 80, 0.3),
-      0 0 3px;
   }
   5% {
-    text-shadow:
+    --crt-shift: 0.717;
-      2.7928974010788217px 0 1px rgba(0, 30, 255, 0.5),
-      -2.7928974010788217px 0 1px rgba(255, 0, 80, 0.3),
-      0 0 3px;
   }
   10% {
-    text-shadow:
+    --crt-shift: 0.008;
-      0.02956275843481219px 0 1px rgba(0, 30, 255, 0.5),
-      -0.02956275843481219px 0 1px rgba(255, 0, 80, 0.3),
-      0 0 3px;
   }
   15% {
-    text-shadow:
+    --crt-shift: 0.103;
-      0.40218538552878136px 0 1px rgba(0, 30, 255, 0.5),
-      -0.40218538552878136px 0 1px rgba(255, 0, 80, 0.3),
-      0 0 3px;
   }
   20% {
-    text-shadow:
+    --crt-shift: 0.893;
-      3.4794037899852017px 0 1px rgba(0, 30, 255, 0.5),
-      -3.4794037899852017px 0 1px rgba(255, 0, 80, 0.3),
-      0 0 3px;
   }
   25% {
-    text-shadow:
+    --crt-shift: 0.414;
-      1.6125630401149584px 0 1px rgba(0, 30, 255, 0.5),
-      -1.6125630401149584px 0 1px rgba(255, 0, 80, 0.3),
-      0 0 3px;
   }
   30% {
-    text-shadow:
+    --crt-shift: 0.18;
-      0.7015590085143956px 0 1px rgba(0, 30, 255, 0.5),
-      -0.7015590085143956px 0 1px rgba(255, 0, 80, 0.3),
-      0 0 3px;
   }
   35% {
-    text-shadow:
+    --crt-shift: 1;
-      3.896914047650351px 0 1px rgba(0, 30, 255, 0.5),
-      -3.896914047650351px 0 1px rgba(255, 0, 80, 0.3),
-      0 0 3px;
   }
   40% {
-    text-shadow:
+    --crt-shift: 0.993;
-      3.870905614848819px 0 1px rgba(0, 30, 255, 0.5),
-      -3.870905614848819px 0 1px rgba(255, 0, 80, 0.3),
-      0 0 3px;
   }
   45% {
-    text-shadow:
+    --crt-shift: 0.573;
-      2.231056963361899px 0 1px rgba(0, 30, 255, 0.5),
-      -2.231056963361899px 0 1px rgba(255, 0, 80, 0.3),
-      0 0 3px;
   }
   50% {
-    text-shadow:
+    --crt-shift: 0.021;
-      0.08084290417898504px 0 1px rgba(0, 30, 255, 0.5),
-      -0.08084290417898504px 0 1px rgba(255, 0, 80, 0.3),
-      0 0 3px;
   }
   55% {
-    text-shadow:
+    --crt-shift: 0.61;
-      2.3758461067427543px 0 1px rgba(0, 30, 255, 0.5),
-      -2.3758461067427543px 0 1px rgba(255, 0, 80, 0.3),
-      0 0 3px;
   }
   60% {
-    text-shadow:
+    --crt-shift: 0.565;
-      2.202193051050636px 0 1px rgba(0, 30, 255, 0.5),
-      -2.202193051050636px 0 1px rgba(255, 0, 80, 0.3),
-      0 0 3px;
   }
   65% {
-    text-shadow:
+    --crt-shift: 0.735;
-      2.8638780614874975px 0 1px rgba(0, 30, 255, 0.5),
-      -2.8638780614874975px 0 1px rgba(255, 0, 80, 0.3),
-      0 0 3px;
   }
   70% {
-    text-shadow:
+    --crt-shift: 0.125;
-      0.48874025155497314px 0 1px rgba(0, 30, 255, 0.5),
-      -0.48874025155497314px 0 1px rgba(255, 0, 80, 0.3),
-      0 0 3px;
   }
   75% {
-    text-shadow:
+    --crt-shift: 0.486;
-      1.8948491305757957px 0 1px rgba(0, 30, 255, 0.5),
-      -1.8948491305757957px 0 1px rgba(255, 0, 80, 0.3),
-      0 0 3px;
   }
   80% {
-    text-shadow:
+    --crt-shift: 0.021;
-      0.0833037308038857px 0 1px rgba(0, 30, 255, 0.5),
-      -0.0833037308038857px 0 1px rgba(255, 0, 80, 0.3),
-      0 0 3px;
   }
   85% {
-    text-shadow:
+    --crt-shift: 0.025;
-      0.09769827255241735px 0 1px rgba(0, 30, 255, 0.5),
-      -0.09769827255241735px 0 1px rgba(255, 0, 80, 0.3),
-      0 0 3px;
   }
   90% {
-    text-shadow:
+    --crt-shift: 0.884;
-      3.443339761481782px 0 1px rgba(0, 30, 255, 0.5),
-      -3.443339761481782px 0 1px rgba(255, 0, 80, 0.3),
-      0 0 3px;
   }
   95% {
-    text-shadow:
+    --crt-shift: 0.56;
-      2.1841838852799786px 0 1px rgba(0, 30, 255, 0.5),
-      -2.1841838852799786px 0 1px rgba(255, 0, 80, 0.3),
-      0 0 3px;
   }
   100% {
-    text-shadow:
+    --crt-shift: 0.673;
-      2.6208764473832513px 0 1px rgba(0, 30, 255, 0.5),
-      -2.6208764473832513px 0 1px rgba(255, 0, 80, 0.3),
-      0 0 3px;
   }
 }
 header,