Which one of the following titles by Valve is not based on a Community Mod?

The title "Ricochet" by Valve is not based on a community mod. Unlike other Valve games such as Counter-Strike, Day of Defeat, and Team Fortress, which originated as mods created by the gaming community and were later acquired by Valve, Ricochet is an original game developed entirely by Valve. It is a multiplayer first-person shooter game that involves players trying to eliminate each other by throwing discs and dodging incoming ones, taking place in a futuristic, sci-fi setting.