Sofa, Meet Stairwell
A three-seater. A concrete spiral staircase. One door at the top. There is no gravity here and nothing is chasing you — the only thing in your way is geometry.
The puzzle
Push it forward with W. The stairs start just ahead.
Third floor. No lift.
Get the sofa up the spiral and out through the door at the top. It will not fit the way you are holding it. That is the whole puzzle.
About this puzzle
Everyone who has ever moved house has had this argument on a staircase. One person is convinced it will go. The other is convinced it will not. Both are shouting. Sofa, Meet Stairwell is that argument, rebuilt in three dimensions, with the shouting removed and the geometry left in.
You are holding a three-seater at the bottom of a concrete spiral. There is a newel column in the middle, a handrail sticking out of the outer wall, treads climbing away under your feet, and the underside of the landing above waiting to catch the top of the backrest. Somewhere up there is a doorway 95 centimetres wide. The sofa is 82 centimetres deep. It goes through — but not the way you are currently holding it.
The move that unlocks the climb is the one real movers make without thinking: tilt it to match the stairs. A sofa held level spans about a hundred degrees of the spiral, which means its far end is nearly a metre lower than its near end, which means something is going to hit something. Tip the nose up to roughly twenty-five degrees and the sofa lies along the helix instead of across it, and suddenly the whole staircase opens up.
The route was verified before release rather than hoped for. A search across sofa position, height, turn and tilt found a continuous collision-free path from the bottom landing to the room at the top, plus a second one for standing the sofa on end and walking it through the door. It is hard. It is not impossible.
How to move it
- Walk it forward flat until the front end reaches the first tread. It will stop there, because the tread is in the way. This is correct.
- Lift and tip. Raise the sofa with R and tip the nose up with the up arrow until it sits along the slope of the stairs rather than across it.
- Turn as you climb. The staircase is curving underneath you the whole time. Feed in Q or E continuously — a spiral punishes anyone who only pushes.
- Mind the handrail. It juts 15 centimetres out of the outer wall at about waist height. Carry the sofa above it or hug the column to stay inside it.
- Duck under the landing. Halfway up, the slab of the top landing crosses overhead and the ceiling drops. Come down and flatten out to slide beneath it.
- Stand it on end. On the top landing, tip the sofa all the way to vertical. Now it is a narrow upright box, and a narrow upright box fits through a door.
Why this exists
The mathematicians have a version of this. It is called the moving sofa problem, and it asks for the largest shape that can be slid around a right-angled corner in a corridor. It has been open since 1966. Nobody is claiming this browser toy solves it. But it does capture the thing that makes the problem stick: the answer is never obvious by looking, and it is always obvious the moment somebody finds it.
Most games about space are about shooting across it. This one is about occupying it. There is no timer forcing you, no failure state, no way to break the sofa. You can stand there for an hour rotating it a degree at a time, and the staircase will wait. The only thing you can lose is your patience, and the only thing you can win is that specific small satisfaction of watching a thing that clearly does not fit go through anyway.
Frequently Asked Questions
What is Sofa, Meet Stairwell?
It is a free 3D browser puzzle about moving day. You are carrying a three-seater sofa up a concrete spiral staircase. Nothing pushes you and nothing chases you — the only thing standing between you and the door at the top is geometry.
How do I control the sofa?
W and S push and pull it along its own length. A and D slide it sideways. Q and E turn it. R and F raise and lower it. The up and down arrows tip the nose. On a phone the same controls appear as buttons under the view.
Is there real physics in it?
There is no gravity and no momentum, because you are carrying the sofa rather than dropping it. What is real is the collision: the sofa is treated as a solid box measuring 1.85 by 0.82 by 0.80 metres, and it simply cannot pass through the newel, the treads, the handrail or the walls. If a move would clip something, the move does not happen.
Is it actually possible to finish?
Yes, and this was checked rather than assumed. Before release a search was run over the full space of sofa positions, heights, turns and tilts, and it found a continuous collision-free route from the bottom landing all the way into the top room. Tilting the sofa to about twenty-five degrees to match the pitch of the stairs is the key to the climb.
What are the scuffs counting?
Every time you hold a direction that the sofa cannot move in, that counts as one scuff against the plaster. It is not a penalty and it does not end the run. It is simply the honest record of how much of the stairwell you damaged on the way up.
Does it work on mobile?
Yes, on any modern phone or tablet browser with WebGL. Turning the phone to landscape gives you a much larger view, which matters here because most of the difficulty is judging clearances by eye.
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