Try to fix the ant problem

src/Renderer.ts

@@ -47,6 +47,10 @@ export default class Renderer {
 
     constructor(public canvas: HTMLCanvasElement) {
         this.renderer = new THREE.WebGLRenderer({ canvas });
+        // clear alpha must be 0: UnsignedByte render targets (antsDiscreteRT) retain
+        // the clear value in pixels not covered by instanced draws. alpha=1 produces
+        // byte 255, which world.frag misinterprets as depositMatId=255.
+        this.renderer.setClearColor(0x000000, 0);
 
         this.initResources();
 
@@ -181,6 +185,7 @@ export default class Renderer {
         );
         scenes.sandPhysics.material.uniforms.uFrame.value = this.frameCounter;
         this.renderer.render(scenes.sandPhysics, scenes.sandPhysics.camera);
+
         this.frameCounter++;
 
         this.setViewportFromRT(this.resources.worldBlurredRenderTarget);

src/materials/registry.ts

@@ -11,7 +11,7 @@ const BUILTIN_MATERIALS: Material[] = [
         name: "air",
         behavior: BEHAVIOR_GAS,
         density: 0,
-        color: [0, 0, 0, 0],
+        color: [0.53, 0.81, 0.92, 1.0],
         hardness: 0,
         angleOfRepose: 0,
     },

src/scenes/ScreenScene.ts

@@ -56,6 +56,8 @@ export default class ScreenScene extends AbstractScene {
     constructor(renderer: Renderer) {
         super(renderer);
 
+        const groundDefines = this.renderer.getCommonMaterialDefines();
+
         const ground = new THREE.Mesh(
             new THREE.PlaneGeometry(1, 1),
             new THREE.ShaderMaterial({
@@ -70,7 +72,7 @@ export default class ScreenScene extends AbstractScene {
                 },
                 vertexShader: vertexShaderGround,
                 fragmentShader: fragmentShaderGround,
-                defines: this.renderer.getCommonMaterialDefines(),
+                defines: groundDefines,
                 glslVersion: THREE.GLSL3,
             }),
         );

src/shaders/screenWorld.frag

@@ -31,7 +31,7 @@ void main()	{
 
     if (a == 0.) t = vec3(0);
 
-    vec3 color = mix(vec3(1, 1, 1), t, a * 0.7);
+    vec3 color = mix(vec3(0.53, 0.81, 0.92), t, a * 0.7);
 
     // non-air cells use material color as base, with pheromone tint
     if (materialId != MAT_AIR) {