Since Valve’s class-based shooter Team Fortress 2 came out in 2007, it has constantly been changing. New maps, hats and weapons are being added all the time, and this summer saw the release of a new co-op mode, Mann vs. Machine. In Mann vs. Machine, six players fight waves of robots, all copies of one of the nine playable classes. Between waves, players can upgrade their equipment with money dropped by killed robots. Thrown in among the normal enemies are giant ones, and an extremely durable tank.

All nine classes from the competitive game are available in Mann vs. Machine, but not all are useful. The Quick Scout is necessary to gather money, and the sentries made by engineers make Mann vs. Machine into something like a tower-defense game. The Stealthy Spy is difficult to use, and the Sniper is nearly useless. When Mann vs. Machine debuted, matchmaking was slow and the game itself was riddled with glitches. The glitches and matchmaking have been fixed, but it’s hard to find a server with six players. Mann vs. Machine is fun but doesn’t match the experience of competitive multiplayer. However, like everything else in Team Fortress 2, it will likely evolve in the future.