…fused, thus:

  float3 worldNormal = normalize(mul(eyeMat, float4(normal,1.0))).xyz;
same basic principle for
      addToResult = lightColor * float4( fLT, 0.0);
fLT is an F3, so tacking on an extra value there matches it to the lightColor  F4, whereas taking a 0 on lightColor would make that an F5