Cleaned up and commented version.

Assets/_Scripts/Eye-Tracking/Not in use test purpose only/_Shaders/GazeOverlay.shader

@@ -0,0 +1,40 @@
+Shader "Hidden/GazeOverlay"
+{
+	SubShader
+	{
+		Tags { "RenderType" = "Opaque" "RenderPipeline" = "UniversalPipeline" }
+		pass
+		{
+			Name "GazeOverlayPass"
+			ZTest Always
+			ZWrite  Off
+			Blend SrcAlpha OneMinusSrcAlpha
+
+			HLSLPROGRAM
+			#pragma vertex VertFullScreenTriangle
+			#pragma fragment frag
+
+
+			#include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
+
+			struct Varyings
+			{
+				float4 positionHCS : SV_POSITION;
+				float2 texcoord : TEXCOORD0;
+			};
+
+			Varyings VertFullScreenTriangle (uint vertexID : SV_VERTEXID)
+			{
+				Varyings o;
+				o.positionHCS = GetFullScreenTriangleVertexPosition(vertexID);
+				o.texcoord = GetFullScreenTriangleTexCoord(vertexID);
+				return o;
+			}
+
+			#include "GazeOverlayPass.hlsl"
+
+			ENDHLSL
+		}
+	}
+	FallBack Off
+}