A perfectly ordinary morning. Then the streets fill with an invisible, silent gas, and everyone below the third floor stops breathing. Build a life above the stilled city — read the breath, descend the dead streets, and rise before the Still does.
Hard-SF vertical survival & societyNothing is rubble. The cars still gleam. The shelves are full. The lights are on. It is all just under the Still — and the Still is patient.
The horror isn't wreckage; it's a pristine world you can see and cannot touch. Every mechanic flows from one reframe: the streets are the dead floor of the world, and you live in the canopy above them.
An invisible, heavier-than-air gas has settled over the streets. Below the line, an entire city sits pristine and silent — a museum nobody can enter.
Spans bridge neighbours into roosts; a drone flock threads the gaps too wide to bridge — light, high-value trade knitting distant clusters together.
Diplomacy, commerce, and conflict travel the guide-wires of the sky.
One invented vocabulary does the storytelling for us — and makes a deep sim readable at a glance.
That's the canon — what the narration and the instruments use. The survivors talk differently: the old hands still call it the sea; the cult calls it the Hush; the kids dare each other to touch the gray. Same world, many tongues.
A ruptured deep-geological carbon-capture reservoir vents CO₂ into the city. It's ~1.5× denser than air, so it pools in the street canyons with a flat, level top.
Invisible. Odorless. Silent. The 1986 Lake Nyos disaster, scaled to a city.
Descend below the line on a rebreather that burns soda lime with every breath you take. Grab what you can; climb out before the air on your back — or the Still — runs out.
The gas that kills you is the currency that lets you descend. One molecule runs the whole economy.
The Still rises and falls with the weather. Every day you read the sky and gamble against it.
The Damp settles low and dense — lower floors briefly reachable. Good for deep descents, bad for cold and no solar.
Convection churns the layer upward, unpredictably, into floors you thought were safe. Stay high.
Scrubs and clears pockets — a chance to descend, or to refill the tanks before the Still returns.
A deep inversion and a fresh vent pulse drive the Damp far above its line for hours. Haul spans higher. Seal floors. Evacuate upward.
Day to day the Still breathes in and out — but over weeks the average breathline rises as the reservoir keeps venting. The 4th floor that was safe in week one is stilled by week eight. You are racing your own verticality against a permanent, rising Still.
Spans aren't snap-to objects. The sim checks tension, the catenary, wind shear, point loads, and fatigue over time. Failure is foreshadowed — a creak, a sway, a frayed strand — never a cheap snap.
The penthouse owns the best solar and the longest sightlines; the low floors live one bad afternoon from being stilled.
Who controls the tallest tower controls the Canopy. The player never does the math — they read the gauges and feel the constraint.
You run errands, buy coffee. The world is pristine and alive. The disaster hits with no cutscene — people drop in the street. You scramble for the nearest doorway and up the stairs. Whatever building you reach is your randomized start.
Survive on what your building holds. Map your vertical prison. Meet — or fail to meet — the others who made it inside.
Supplies run out. Rig a rebreather and descend the stilled floors and neighbours for food, water, meds, tools — and the instruments that let you read the breath.
Bridge to adjacent buildings. Roof gardens, rainwater, solar, workshops. Take in survivors; manage skills, morale, and politics. You're a community now.
Spans and a drone flock knit distant clusters together. Diplomacy, trade, conflict. Then an ending: outlast the vent, escape over the breathline, or cap the reservoir itself.
Dread from physics and weather. No combat needed to be terrifying.
Damp, Still, breathline, descent — a complex sim made instantly readable, with character slang layered on top.
A closed economic loop that's mechanically tight and thematically perfect.
The unsettling beauty of a pristine city stilled in silence — a look almost nobody has.