From 43e510341eedc94f9173446bc3e01d9229942742 Mon Sep 17 00:00:00 2001
From: LucaP <luca.pislaru@protonmail.com>
Date: Sat, 5 Sep 2026 12:36:34 +0300
Subject: [PATCH] feat: weave a flowing multicolor palette through the terrain
 grid

---
 src/scene/world/terrain.ts | 29 +++++++++++++++++++++++++----
 1 file changed, 25 insertions(+), 4 deletions(-)

diff --git a/src/scene/world/terrain.ts b/src/scene/world/terrain.ts
index 5b4e2a9..9761801 100644
--- a/src/scene/world/terrain.ts
+++ b/src/scene/world/terrain.ts
@@ -84,6 +84,19 @@ export function createTerrain(
       varying float vDepthFade;
       varying float vFlow;
       varying vec3 vTerrainPosition;
+      varying vec3 vGridColor;
+
+      // A closed palette ribbon: its ends meet in cyan so travel never
+      // produces a color seam. Compute it per vertex, not per pixel.
+      vec3 gridSpectrum(float phase) {
+        float p = fract(phase);
+        vec3 cyan = vec3(0.025, 0.70, 0.90);
+        vec3 color = mix(cyan, vec3(0.075, 0.18, 0.80), smoothstep(0.04, 0.22, p));
+        color = mix(color, vec3(0.39, 0.085, 0.80), smoothstep(0.22, 0.40, p));
+        color = mix(color, vec3(0.88, 0.035, 0.28), smoothstep(0.40, 0.60, p));
+        color = mix(color, vec3(0.95, 0.21, 0.08), smoothstep(0.60, 0.78, p));
+        return mix(color, cyan, smoothstep(0.78, 1.0, p));
+      }
 
       float hash21(vec2 point) {
         point = mod(point, 256.0);
@@ -127,6 +140,12 @@ export function createTerrain(
 
         vHeight = clamp(height / max(1.0, uRelief), 0.0, 1.0);
         vRoadMask = roadMask;
+        // Signed lateral variation gives each bank its own color rhythm.
+        // Whole longitudinal cycles preserve the existing terrain wrap.
+        float chroma = world.y * ${(31 / NOISE_PERIOD).toFixed(10)}
+          + position.x * 0.014 + height * 0.025
+          + 0.12 * sin(world.y * ${((Math.PI * 2 * 17) / NOISE_PERIOD).toFixed(10)} + position.x * 0.028);
+        vGridColor = gridSpectrum(chroma);
         vec4 viewPosition = modelViewMatrix * vec4(displaced, 1.0);
         float viewDistance = -viewPosition.z;
         vDepthFade = smoothstep(4.0, 18.0, viewDistance)
@@ -148,13 +167,15 @@ export function createTerrain(
       varying float vDepthFade;
       varying float vFlow;
       varying vec3 vTerrainPosition;
+      varying vec3 vGridColor;
 
       void main() {
         float ridgeMix = smoothstep(0.025, 0.29, vHeight);
-        vec3 valley = mix(uLowColor, vec3(0.10, 0.64, 1.0), uOverdrive * 0.55);
-        vec3 crest = mix(vec3(0.7, 0.025, 0.22), vec3(1.0, 0.12, 0.065), uOverdrive * 0.75 + vFlow * 0.18);
-        vec3 color = mix(valley, mix(vec3(0.28, 0.06, 0.52), crest, ridgeMix), ridgeMix);
-        color = mix(color, uHighColor, 0.13);
+        vec3 color = mix(vGridColor, uLowColor, 0.06);
+        // Speed warms passing accents, while the full palette stays present.
+        float hotAccent = uOverdrive * smoothstep(0.62, 1.0, vFlow) * 0.36;
+        color = mix(color, vec3(1.0, 0.28, 0.10), hotAccent);
+        color = mix(color, uHighColor, ridgeMix * 0.055);
         color = mix(color, mix(uFogColor, uHazeColor, 0.2), 1.0 - vDepthFade);
         float pulse = 0.88 + 0.12 * smoothstep(0.16, 0.55, vFlow);
         float routeCalm = mix(1.0, 0.9, smoothstep(0.82, 1.0, uRouteProgress));