Short but free (even without microtransactions) really fun coop tactical top-down shooter. It runs on source engine and has great re-play potential. I look forward to playing sequel. 7-/10

I used to play more of this on an old account. But the sad truth is - it's a dead game. When it was around - it was average at best. But now it's just a waste of time, and a waste of space.

Alien Swarm is an excellent game with loads of potential, but I must highlight that there is an even better and newer version available named Alien Swarm: Reactive Drop. It is also free and accessible on Steam. While both games are essentially the same, Reactive Drop offers numerous improvements, including additional campaigns, updates, PVP mode, and continued support. If you are a fan of Alien Swarm, I highly recommend giving Alien Swarm: Reactive Drop a try. Now, returning to the original Alien Swarm, it's a prime example of how a fantastic game can be left to decay over time. Despite this, it still provides a pure, enjoyable experience, especially when playing with friends. Although there is only one official campaign, the community has created numerous fan-made campaigns that enhance the game's replayability. However, it's essential to note that the player population in Alien Swarm might be relatively low. This is due to the significant draw towards Reactive Drop, which offers more content and features, leading players to migrate to the newer version, which as I said, is pretty much the same game. In summary, Alien Swarm is undeniably fun, and I encourage trying it out, particularly for the official campaign and the fan-made content. But if you're seeking a more updated and enriched experience, don't hesitate to give Alien Swarm: Reactive Drop a shot, as it builds upon the foundation of the original game and provides a superior gameplay experience.