Developed by Homeworld Remastered core team members, Complex is scripted from scratch, improves the complexity of the original Homeworld gameplay to extent, where player has to take into account a lot of variables during space battle in order to prevail.
1) extract Complex122.zip inside ...Homeworld\HomeworldRM\Data (both "Complex122.big" and the folder "locale" must be there)
2) right click the HomeworldRM shortcut, select properties, select shortcut, add -mod Complex122.big at the target command line (if you don't have a shortcut create it by ...Homeworld\HomeworldRM\Bin\release\HomeworldRM.exe)
3) run the game by your HomeworldRM shortcut (don't use the Steam launcher)
4) it's recommended to play the english version, Complex is not localized