What is Dosun-Fuwari?

Dosun-Fuwari (ドスンフワリ) is a beloved physics-based logic puzzle published by Nikoli. The name comes from Japanese onomatopoeia for a heavy thud ("dosun") and gentle floating ("fuwari"). Each outlined room contains exactly one sinking iron ball and one floating balloon.

Where can an iron ball rest?

An iron ball must sink until it rests on the floor (bottom row of the grid), directly on top of a black wall block, or on top of another ball or balloon.

Where can a balloon float?

A balloon must float upwards until it touches the ceiling (top row of the grid), directly beneath a black wall block, or directly beneath another ball or balloon.

Can two circles touch horizontally?

No. Two circles (balls or balloons) can never be side-by-side in adjacent columns within the same row.

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Dosun-Fuwari

Easy

Iron balls sink to the floor, balloons float to the ceiling!

TIME:0:00

MOVES:0

▲ CEILING (BALLOONS FLOAT HERE) ▲

▼ FLOOR (IRON BALLS SINK HERE) ▼

Mastering Dosun-Fuwari: Gravity & Buoyancy Strategy

Published by Nikoli, Dosun-Fuwari is one of the most playful puzzles in the Japanese catalog, simulating the natural physics of heavy iron spheres and light helium balloons.

The Laws of Buoyancy & Mass

Room Quota: Each room must contain exactly 1 Iron Ball (\(\bullet\)) and 1 Balloon (\(\circ\)).
Iron Ball Gravity: An iron ball cannot hover in empty space. It must sink straight down to the floor, onto a solid wall, or onto an object beneath it.
Balloon Lift: A balloon cannot linger in mid-air without support. It rises to the ceiling, beneath a solid wall, or beneath an object above it.
No Side-by-Side Clashes: Two circles (whether ball or balloon) can never be adjacent horizontally. Vertical stacking is completely legal!

Deduction Techniques

Inspect narrow rooms that only touch the ceiling or floor at a single cell: if a room has only one cell in the top row, the balloon must float there! Check horizontal exclusions: placing a circle in cell \((r, c)\) immediately rules out \((r, c - 1)\) and \((r, c + 1)\).