Valve is updating Team Fortress 2's Mann vs Machine mode, and it wants your help

Valve is planning a new Team Fortress 2 Mann vs. Machine update, more than a decade after the co-op game mode came to the team-based shooter. The Half-Life and Counter-Strike maker is also asking TF2’s community to make and submit maps and missions, which suggests that plenty of player creations will expand MvM, all these years later.