The Red Solstice is free on the Humble Store

The Red Solstice is a sci-fi, squad-based survival game in which a squad of four space marines cleans house in a Martian colony installation that's been overrun by alien horrors from the fifth dimension. (Or someplace like it, anyway.) It has a beefy single-player campaign and a co-op mode for up to eight players, with randomized missions and events set across six large maps. It is also free on the Humble Store, as part of the Humble Winter Sale, for the next two days. 

Head to the Red Solstice listing on the Humble Store, click the "add to cart" button, and then proceed to the checkout. If all has gone well, you will see a blue "Get it for free!" button on the checkout page, so what you want to do next is click on that. An email will be sent your way containing the remaining instructions, or if you're in a hurry you can just hit the "preview your email" button. Either way, you'll end up with a Steam key that can be redeemed directly through the Humble site, or manually copied-and-pasted into Steam if that's your thing. 

Released in 2015, The Red Solstice is the predecessor to last year's Solstice Chronicles: MIA, a more action-oriented twin-stick tactical shooter that came out last year. There aren't a lot of players so putting together an eight-man squad might be tough, but it did pretty well for itself critically and has "mostly positive" user reviews on Steam. It's also free, which is a pretty solid selling feature. You've got until 10 am PT/1 pm ET on January 17 to grab it. 

Some online stores give us a small cut if you buy something through one of our links. Read our affiliate policy for more info.