A Single Breath

About this game

A one-button physics puzzle about rising from the deep in a single breath. You are a bubble, and you own exactly one control: hold to rise, release to brake. Letting go does not mean falling — the bubble slows to a gentle drift, so you can hold your height and wait. Wait too long, though, and it really does sink. Every barrier above you runs on a fixed cycle with no randomness at all: pairs of slabs slide together and apart, the gap never moves sideways, and the whole problem is reading the beat. There are five kinds of barrier — the gate, the camera-like iris, the fast hammer, the stacked slide gate, and the crumb layer, which shatters instead of killing you, so smashing through it is a legitimate move rather than a mistake. Eighteen levels in four chapters, and not one of them can be beaten by simply holding the button down. Every level is machine-verified to be passable, and a hint button will tell you what the next few seconds should look like. No download, no sign-up.

How it plays

• One button, three states: hold and the bubble climbs at a steady 7.2 units a second; the instant you let go it brakes to a gentle drift, so you can park in mid-water and wait; hold the brake past about a second and it starts to sink in earnest. There is no left, no right, and no jump to fall back on.
• Every barrier is a door, never a wall: the slabs slide together and apart and the gap is fixed in the middle of the channel. It never sweeps sideways, so the only thing you ever have to solve is when, not where.
• Nothing is random. Each barrier runs on a fixed period, so every death can be replayed frame for frame — watch one full cycle, then move on the open beat. The later levels deliberately mix periods that never line up, which is what forces you to wait instead of rushing.
• Five mechanics, four chapters: the gate that simply opens and closes, the iris whose opening breathes wide and narrow, the hammer on a much shorter cycle, the stacked slide gate you have to pass twice, and the crumb layer of packed earth — which shatters instead of killing you, making a deliberate smash a real move.
• Eighteen levels, each machine-verified before release. The verifier runs three controllers against every layout — a main "read the cycle" policy, a deliberately cautious one, and a naive one that just holds the button forever. A level is only accepted if the first clears it, the cautious one clears it inside a sane time, and the naive one fails.
• Because the simulation is a small fixed-step integrator with no server and no assets to download, the first level is interactive the moment the page paints, and the whole game ships in a single on-demand chunk that only the play page ever loads.

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