If you’re one of the four gamers out there who hasn’t yet played Team Fortress 2, now is the time to do so. Game developer Valve is letting gamers play the game for free for a week ahead of a massive content patch.

The new “Uber” update features extra pieces of equipment for some of the character classes. The company is also teasing a “meet the” short video, which is a funny series that introduces the characters that players take control of in Team Fortress 2. As usual, the update features ridiculous weapons and the video promises to be another hilarious take on the first person shooter (FPS) genre. The game’s style, which regularly mocks a lot of tropes common in the FPS genre, is part of the reasons it’s so successful.

The game will be free to download and play through Sunday. Team Fortress 2 is a multiplayer FPS game that lets players team up in huge capture-the-flag and king-of-the-hill style matches. Players can choose from one of several classes that all fulfill certain roles, like the speedy scout who is good for carrying intel (the game’s version of a flag) or the medic, who can heal and supercharge friendly players. It’s one of Valve’s unusual stunts to try to pick up additional gamers, even though the game is already incredibly popular.

The game is one of only a few on the market right now that thrives on team-based gameplay rather than single-person heroics. Most multiplayer FPS games include team-based deathmatch games — where the team with the largest number of kills wins — but don’t encourage a lot of teamwork in pick-up and casual matches. In Team Fortress 2, teamwork is essential — even for casual gamers who just want to play a quick match during a lunch hour.

It’s also an unusual FPS game because of the artistic direction. Instead of ultra-realistic graphics like those seen in the Battlefield and Call of Duty franchises, the game looks like a cartoon brought to life. Characters have exaggerated features, such as the heavy and his massive minigun and huge muscles. They all have personality quirks too — for example, the sniper is built off a Crocodile Dundee-style Australian hunter.

But despite its quirks, Team Fortress 2 is critically acclaimed and was a large factor in the success of the Orange Box, a collection of five games that Valve released in 2007. The collection included Half Life 2, along with sequels Episode 1 and Episode 2, Team Fortress 2 and the smash hit Portal. It’s currently the highest rated PC game of all time on review aggregating site Metacritic.