GOG, the game store formerly known as Good Old Games, is kicking off its summer sale with a two-day giveaway of classic shooter / RPG System Shock 2. If you launch GOG through its Galaxy desktop client, you can claim a copy from inside it. GOG says this is its way of getting more people onto Galaxy for a stress test, but you should be able to play the game just fine without it, since GOG doesn't lock down its software with copy protection.

If you haven't already played System Shock 2, I've written before about why I love it. It's a creepy, complex, and incredibly memorable game that's held up well since it was first released in 1999 — fans have also made mods that upgrade the graphics, models, music, and other elements. And playing the first System Shock is totally optional, although it's been deeply discounted for the sale as well.

GOG's summer sale also offers three more free games — 2D platforming game Spelunky, the "reimagined" version of adventure game Gabriel Knight: Sins of the Fathers, and a season pass for the episodic Dreamfall Chapters. But to get them, you'll need to earn experience points by doing things like making GOG wishlists and sharing the sale on social media. Whether that's worth it is up to you, but seriously, go check out System Shock 2 already.