The best new game I've played all year is a 30-minute demo where I just climbed rocks and ate chocolate bars – and I still care about it more than Borderlands 4 and GTA 6 combined

Here, I feel like it's just me and the cliff face. Every inch of my body, every minute of my life, is devoted to this fact. Should I reach high and dig my cracking fingernails into that faraway groove? Or do I trust my rough palm enough to grip the smooth stretch of rock in front of me? I spend a few seconds that feel like forever worrying about the decision, and then I barely hear the muffled firetruck sirens outside, reminding me that I'm playing climbing sim Cairn at Tribeca Film Festival in Manhattan.

It's a miracle that Cairn could get me this immersed in the 30 minutes that make up its demo, which is currently available on Steam ahead of the game's November 5 release on PS5 and PC.

I'm not exaggerating when I say, before playing it, Cairn didn't appeal to me at all. Having been raised in Queens and on Long Island, I don't consider myself particularly outdoorsy apart from my tendency to take 10,000-step strolls by the beach.

Cairn, in contrast, is hardcore. Pouty protagonist Aava – who wraps the entirety of her inhumanly flexible arms and legs in climbing tape, making her look like Cleopatra's agile mummy – wants to be the first person to summit Mount Kami. Heading toward it in the demo, I get warmed up with help from my beguiling "Climbot," or climb-assisting robot, that moves like a dancing spider by Aava's side, collecting supportive pitons, letting her off belay to recover energy, and facilitating phone calls with encouraging friends Aava doesn't really want to speak to.

No, Aava is all discipline – she's not chatty, and there doesn't seem to be anything indulgent about her, aside from the chocolate bars she nibbles on to solve her hunger and earn powerful buffs, like improved stamina.

But Aava isn't indestructible. The backpack that holds the candy – along with pain meds, foraged herbs, and other survival essentials – might as well be an external heart.

The bag – along with the vulnerable, wobbling pile of rope, water, and mattress padding strapped to it – can shred Aava's health bar even when she's simply speedwalking, giving me visual cues for how hard I'm pushing my testy protagonist. Even so, her mission would be dead fish without the burden.

The only time Aava appears to relax is when she get to unroll that thin spread of mattress and set up temporary shelter at bivouac points, sleeping off the day's climb until she gets too thirsty to ignore.

In the morning – or at dusk, with a flashlight – it's back to being a mountain goat, slowly and thoughtfully dragging an arm, then a leg, then the other leg, then the other arm up microscopic ridges in the cliff as Aava's body quivers from the strain and her breath starts to sound painful. After driving a piton perfectly deep into the rock with a skill check, I take a swig of pre-boiled water.

Cairn never lets me forget how physically and mentally draining it is to be Aava. Though comic book artist Mathieu Bablet brings lavish greenery and orange juice sunrises to Furi studio The Game Bakers' climbing sim, the Cairn demo is only as romantic as the sharp edge of a boulder. Maybe it's tucked into a bed of perfect snow, and maybe, if you fell, it could split your forehead like a piece of driftwood.

But though the environment is unsympathetic, and Aava and I couldn't be more obviously different – I go to sleep in vintage chiffon nightgowns, and Aava goes a few days without showering – I see half of myself in her.

Stubbornness, abrasiveness, avoiding kind messages and phone calls; when you convince yourself it's better to be alone than misunderstood, life is lonely from the tallest point on Earth. But, in playing Cairn – which has already proven itself to be magnificently pensive in its little demo – Aava and I come together. We were never truly alone, were we?

"Climbing is in itself a game, with rules everybody knows": Cairn's tense, strategic ascents are making our palms sweat.