uniform half4 testInputs;  // equals (-1.25, 0, 0.75, 2.25)
uniform half4 colorGreen, colorRed;

half4 main(float2 coords) {
    // NOTE: the ES3 spec does not mandate NaN support. This test may not succeed on some GPUs.

    half4 valueIsNaN    = 0 / testInputs.yyyy;
    half4 valueIsNumber = 1 / testInputs;

    return (    (isnan(valueIsNaN.x))       &&
             all(isnan(valueIsNaN.xy))      &&
             all(isnan(valueIsNaN.xyz))     &&
             all(isnan(valueIsNaN.xyzw))    &&
            !   (isnan(valueIsNumber.x))    &&
            !any(isnan(valueIsNumber.xy))   &&
            !any(isnan(valueIsNumber.xyz))  &&
            !any(isnan(valueIsNumber.xyzw))) ? colorGreen : colorRed;
}