The Alters is a great game. It’s also a highly stressful one, and that stress kept me coming back for more when I checked it out last year. Set on a hostile world where Jan Dolski, the lone survivor of a spaceship crash, has to make alternate reality clones (”alters”) of himself to survive, the action in The Alters never relents. Your base will fall apart, your Alters will argue and rebel, and nighttime brings threatening radiation that’ll knock you on your ass.

The biggest stressor is the planet’s sun, which will burn everything it shines upon. Jan and his alters are constantly trying to outrun it with their big wheel-shaped space base lest they, ya know, burn to a crisp. That constant ticking clock brings stress, but also meaning — make the wrong decision, allocate the wrong resources, waste too much time and all the Jans will perish. Impending death-by-sunrise is missing in The Alters’ new expansion, making it a much hollower experience. That said, getting to know new Jans and investigating the expansion’s mystery still make it an enjoyable time.

The Alters: Last Variable takes place after the main game’s campaign. Jan and his alters have left the hostile world, but Jan Scientist has stayed behind to investigate the Oasis, an area of fertile land that has somehow survived the burning sunrises. Claiming the rebel Jans’ base as his own, he hunkers down and does what he does best: science!

Interestingly, you don’t actually play as Jan Scientist from the main game, but as an alter of Jan Scientist. The original scientist spent decades working on the base and exploring the Oasis, but plenty of his time was spent simply trying to survive alone; you learn at one point that he was actually trapped outside the base and inside the Oasis for a whole 13-year cycle. It’s an interesting set-up, playing as an alter of an alter, and a great workaround to making sure elements of the base game don’t get repeated. That pesky brain damage issue from Act 2? The original Jan Scientist solved it; this new Jan Scientist can get straight to investigatin’.

With a passion for science, Jan Scientist does exactly that. The whole goal of The Last Variable is learning why the Oasis survives, and seeing if you can replicate it. By building and placing terraformers, regions of the planet’s surface can be granted a lease on life in between cycles of heat-death. When you and your alters wake up from cryosleep, beautiful green swaths of land with purple flowers await. More and more discoveries can be made each cycle, and I’m always curious as to what curveball is about to get thrown Jan’s way next, even if a lot of the science-y mumbo jumbo is lost on me.

As interesting as the Oasis is, the new Jans are the real heart of The Last Variable: Jan Biologist, Chemist, Geologist, and Physicist all feel like unique individuals. Jan Geologist is a carefree scientist wanting to conduct wild experiments, while Jan Biologist is much more down on himself. I’ve enjoyed Jan Physicist’s questline as I helped him realize how much of a jealous prick he was toward his more intelligent assistant; he almost dies after running away because that thought was too much to bear.

Perhaps because they’re off-shoots of Jan Scientist, the new alters are much less angry and rebellious than original Jan’s alters; no one’s randomly called me an asshole just for existing. Or maybe their general calmness comes from the fact that there’s no real sense of danger in The Last Variable.

Unlike the base game, the fiery sunrise is completely avoidable in The Last Variable. Just go to cryosleep when it burns the planet and wake up in 13 years, fresh as a daisy. I haven’t had to reset from an earlier save or plan my days down to the hour because there’s no urgency now. Haven’t yet finished a quest? Eh, it’ll still be waiting for Jan on the other side of the sunrise. Don’t have enough resources to build a terraformer? Just do it in the next cycle and immediately go back to cryosleep. In fact, the only time I’ve gotten a game over screen so far is by accident; I went to sleep in my captain’s cabin instead of the cryosleep chamber out of muscle memory and the sun burned me. I lost all of three minutes reverting to the previous save.

The lack of a ticking clock makes me go through the motions of mining, cooking, researching, repairing, and assigning my alters tasks. I don’t need to be decisive with my actions because there’s no consequence.

I’m also not too worried about keeping my alters happy. Whereas in the base game keeping them well fed and happy is vital to success — an alter’s work shift won’t be very long if they’re angry, and we gotta work, y’all — in The Last Variable, I don’t really care if they’re angry and not working. There’s not much we need to do!

At a certain point, I’m just doing any random activity to pass the time while a specific resource passively collects, before I can move on to the next research project or build the next necessary device. Most revelations happen after initiating cryosleep, meaning I’ve cut cycles short just to advance the plot.

Despite this, I’m still enjoying The Alters: Last Variable. I’m finding myself unable to leave the couch for hours when I sit down to play, as the monotony of its gameplay is oddly calming. The new Jans are great, and Alex Jordan once again delivers standout performances for all of them. The Last Variable has an enticing central mystery, and fans of the base game will enjoy its revelations. Investigating that mystery just leaves me a little unsatisfied without a stressful sun bearing down on me.

The Alters: Last Variable is out now on PlayStation 5, Windows PC, and Xbox Series X. The game was reviewed on PS5 using a prerelease download code provided by 11 Bit Studios. You can find additional information about Polygon’s ethics policy here.