For a limited time you can get all the XCOM games for just $10—yes, even that one

When it comes to turn-based tactics, there's still one undisputed king of the genre: XCOM. If you've never experienced its brand of tense, alien-killing strategy before—or if there's a game or two in the series you skipped—then the good news is that today is a very cheap day to catch up.

Humble Bundle's new XCOM Complete offer is appropriately named—it really does include every XCOM game for just $10/£7.51. Well, technically excluding the mobile game. And that one Hasbro made where you played by email or something. But all the real ones!

Most importantly, that includes both XCOM: Enemy Unknown and XCOM 2, and all the DLC for both. Those two games with their big expansion packs (Enemy Within and War of the Chosen respectively) are an absolute treasure trove in their own right, offering 100s of hours of best-in-show turn-based tactics.

But you also get the spin-offs too. Chimera Squad is well worth a go—it's a more bite-sized take on the formula with a more comic book-y feel, and while it never reaches the heights of the mainline games, it's got a lot of fun ideas. It's an interesting precursor to Marvel's Midnight Suns, too, experimenting with some of the concepts that would go on to play a major role in that game.

The Bureau: XCOM Declassified is a bit more controversial. Before XCOM: Enemy Unknown rebooted the series for modern audiences, 2K thought the right path to bringing it back was a third-person shooter set in the 60s. It ended up releasing a year after Enemy Unknown, thanks to a troubled development, and… well, let's say it wasn't well received. But hey, a fun curiosity to have in your library, and it does have some cool visual design.

And if you really want to dive back into the history of the series, the bundle also includes the original five X-COM games from the 1990s. I can't speak personally to how well these hold up, but there are plenty of fans who prefer the more detailed and in-depth style of the old series—as more recently emulated by the Xenonauts games.

$10/£7.51 gets you the full bundle, and that's definitely the tier I'd recommend going for if you don't already own Enemy Unknown and XCOM 2. The next tier down is $7/£5.26, but for the sake of saving a few bucks, it's a bit of an awkward selection, taking it down to just the old games, The Bureau, and Enemy Unknown with its expansion but without its smaller Slingshot DLC.

And if you just want the old games—which a lot of us probably are missing from our libraries—you can get the five of them at the lowest tier for just $3/£2.25.

All of the games in the bundle are delivered as Steam keys, which makes things nice and easy. And a portion of the proceeds go to a good cause: the Michael J Fox Foundation for Parkinson's Research.

By my calculations the offer ends May 18th—so make sure to grab it before then. Well, assuming you're not part of the 95% of PC Gamer readers who already have a 500 hour save file in XCOM 2.