Instead of telling you about this game, I'm going to tell you a story.

In November 2009, I bought TF2 for $20. It was my first Steam game.

The next year, I won a Steam Sale raffle (they used to do these) and got the top 5 games on my wishlist for free. Garry's Mod, Half-Life 2, EP1, EP2, and Portal 2. Yes, this was long before Portal 2 was available for preorder.

I became aware that I could get a free TF2 hat if I played Alien Swarm, so I tried it out. This was back on a machine that couldn't handle the shaders in this game that I'm now running a decade later on an RTX 2060. And you know what? I liked this game.

So if you're reading this to find out whether you should try Alien Swarm, here's the answer in the middle of this story: Maybe. It's definitely worth playing it if you want the TF2 hat, but even though this game is very good, it is over a decade old. But it's not just a game...

Alien Swarm comes with the Alien Swarm SDK, which has a map editor, engine tools, a few of the maps from the game in an editable form, and most importantly, enough of the game's source code to build your own copy. I had previously played around with the Source SDK, but with that the starting point was a sample mod named SDK Base, not Half-Life 2 or Team Fortress 2 or Portal.

The fact that Alien Swarm was open source and also completely free meant that people like me could get into game development by starting with an essentially already-complete game. The separation of the client and server in Source Engine also meant that each could be modded separately - you could create a server-only mod like chicken's c00p and ASBI, or a client-only mod that just improved the HUD, and still play with people with the vanilla version of the game.

And of course I tried my hand at modding, with a few unsuccessful projects. And then one very successful project. Again, you might be able to find it if you look for it. It's certainly not hidden.

Over time, Valve added more features to Steam. Proton. Broadcasts. Inventory. The Workshop was a big one. People had been publishing their Alien Swarm addons and mods on various websites, but sometimes those websites shut down or the files became unavailable for other reasons. People wanted Workshop support. I wanted Workshop support. But wait, couldn't I add Workshop support? As it turns out...

This game's 94% review score over tens of thousands of reviews is not an accident. It's a good game, and it's free. You probably got that much before you read this far into my review. The game is just as good as it was a decade ago (with the 480p default resolution to show it). But if you're not here for a TF2 hat and you're looking for a better version of Alien Swarm on Steam, you don't have to look far. And maybe after that, you'll come back here, and see how far we've come. A lot of things can happen in a decade.