I think the website sums it up best:
Firearms: Source is a high adrenaline First Person Shooter that emphasizes precision aiming, high mobility, and team-based strategy. Firearms: Source is a return to the classic shooters of the 90′s where the games had higher learning curves and a greater rewards for mastering the game mechanics. While our guns provide a sense of immersion unrivaled by even the most popular of retail shooters, our gameplay remains a fast paced deathmatch unrestricted by realism.
I was responsible for writing a large portion of the weapon handling and behaviors, gameplay/rules, animation state machines, scripting hooks for game designers, the weapon and body attachment/customization systems, entities for level designers, material proxies for artists, screen-space (and some world-space) effects, HUD, and UI. All of this was written mostly in C++ using a little bit of C when and where required. The initial IDE of choice was Visual Studio 2010 but myself and the other programmers moved to Visual Studio 2012 later on.
This one is probably the best-produced video of the game, done by one of our testers. I can't embed it here because embeds are disabled for this video, but I seriously encourage you to watch it: FireArms Source Mini