(en) Al Bickham, « The Story of X-Com : From the school playground to Laser Squad Nemesis in the words of Julian Gollop. », sur Eurogamer, (consulté le ) : « Julian Gollop: Microprose wanted us to do a sequel in six months. We told them the only way we could do a sequel in that timeframe would be to change the graphics and tweak a few bits. Eventually we came to a compromise: they'd license our code to make a direct sequel, and we'd do the third one in the series in two years. TFTD was made entirely by Microprose; we had no input apart from giving them our code. They managed to do it in a year, but they had a much bigger team. A shockingly large team, I thought at the time, 12-15 people. ».
(en) Ron Dulin, « X-COM: Terror From the Deep Review », sur GameSpot, (consulté le ) : « Apart from new art and a handful of new combat options, this is exactly the same game as UFO Defense, only much more difficult. ».