XGC-1 Xtreme Greenhouse Controller The XGC-1 is the best all in one controller ever made. The specifications of the XGC-1 are identical in every way to the CGC-1, except for the addition of Fuzzy Logic(tm) CO2 control built in! Fuzzy Logic(tm) can be compared to a good driver. As a good driver approaches a red light, he or she applies the brakes to gradually slow down BEFORE getting to the intersection. Fuzzy Logic(tm) uses the same idea to keep the CO2 level at your desired setting, without going over the set point.