The purpose of f.lux is to simulate a natural biorythm. Playing extremly fast and immersive action games at night is w´the bigger problem here, I'd say.
doesn't always work tho, at least didn't work for me in QL, but may have been something in my cfg preventing it from considering it fullscreen. and tbh it looked pretty cool, I bet it would make q1 look a bit more sandstone :o