Make effects react to audio much more visibly (brightness pulse, beat flash, bass zoom)

The visuals received the audio correctly but modulated only small terms, so the
reaction was subtle versus the clearly-moving meters. Strengthen the universal
audio response in the shader without touching meter calibration.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/shaders.js

@@ -378,12 +378,13 @@ vec3 colorize(float v, vec2 uv0) {
   vec3 hsv = rgb2hsv(mix(uColorA, uColorB, v));
   hsv.x = fract(hsv.x + uHueBase + uHueCycle * uT + uTreble * 0.06 * aMix);
   hsv.y = clamp(hsv.y * uSat, 0.0, 1.0);
-  hsv.z = pow(clamp(hsv.z, 0.0, 1.0), uContrast) * (0.7 + 0.6 * uLevel * aMix);
+  // Brightness clearly pulses with the loudness and punches on the beat.
+  hsv.z = pow(clamp(hsv.z, 0.0, 1.0), uContrast) * (0.5 + 1.3 * uLevel * aMix + 0.6 * uBeat * aMix);
   vec3 col = hsv2rgb(hsv);
   if (uInvert > 0.5) col = vec3(1.0) - col;
   // For silhouette/meter effects, fade the empty field to black.
   col *= mix(1.0, smoothstep(0.0, 0.04, v), uBgDark);
-  col += uBeat * 0.18 * aMix;
+  col += (uBeat * 0.35 + uLevel * 0.12) * aMix;
   col *= 1.0 - 0.28 * dot(uv0, uv0);
   return col;
 }
@@ -393,7 +394,7 @@ void main() {
   aMix = uAudioMix;
   vec2 uv0 = (gl_FragCoord.xy - 0.5 * uRes) / uRes.y;
   vec2 uv = rot(uRot + uRotSpeed * uT) * uv0;
-  uv /= (uScale * (1.0 + uBass * 0.4 * aMix));
+  uv /= (uScale * (1.0 + uBass * 0.8 * aMix));
 
   if (uSym > 0.5) {
     float a = atan(uv.y, uv.x), r = length(uv);