There is an easy way to distinguish ISA weapons from Helghast weapons. ISA weapons feature a green scope/eye-piece (if present) and have the standard fiery colored muzzle-flash. Helghast weapons feature a red scope/eye-piece (if present) and have a light/sky blue colored muzzle-flash. Helghast weapons also commonly feature a barrel-like magazine as opposed to the ISA weapons which feature the standard shaped magazines seen on most modern day weapons.
To speed up the animation process, the team shot 'animatics' for all the cut-scenes in the game using a video-camera and a bunch of actors, consisting of people from the development team and a few hired extras. Empty cardboard computer boxes were used to construct simple sets, with brooms and toy guns used as props.
The original 'Helghast March' music was recorded with the Moscow Symphony Orchestra before the actual game went into production, as part of a pitch to Sony. Years later the rest of the music was recorded with the Prague Philharmonic and Chorus as the game neared completion.
As Holland has strict gun laws, it proved difficult for the sound designers to get their hands on real-life weaponry. Instead, various staplers and other pieces of office equipment where recorded and treated to sound like the reloading action of guns.