How to play
Ball Sort
Also known as Ball Sort Puzzle, Bubble Sort Color Puzzle, Color Ball Sort, Sort Balls Puzzle
- 100K+ downloads
- On Google Play since 2021
- Free to play
What is Ball Sort?
Ball Sort is a stacking logic puzzle played with tall tubes holding coloured balls in scrambled order. You may only lift the top ball of a tube, and you may only drop it onto a ball of the same colour or into an empty tube. The challenge is that every ball you move sits on top of another, so the order in which you unstack matters far more than which colour you happen to like.
How to play Ball Sort
Setting up the board
You are given a row of tubes, most of them filled to the top with balls of mixed colours, plus one or two empty tubes. Each tube usually holds four balls, and every colour appears exactly enough times to fill one tube. Later levels add more colours and more tubes, never new rules.
How it works
- Tap a tube to lift its top ball, then tap another tube to drop it there.
- Only the top ball of a tube can move; balls beneath it are locked in place.
- A ball may be dropped only onto a ball of the same colour, or into a completely empty tube.
- The destination tube must have a free slot - full tubes cannot accept anything.
- Balls move strictly one at a time, so a run of three matching balls takes three separate moves to relocate.
- Balls are never added, removed or recoloured; the puzzle is pure rearrangement.
- Undo reverses your last move, within whatever limit the level allows.
How to solve
The level is complete when every tube is either filled with balls of one single colour or completely empty, with no mixed tube left.
Solving tips
- Treat an empty tube as your most valuable asset. Because balls move singly, an empty tube is the only place a wrong-coloured ball can go, and it is what lets you unbury a colour.
- Read the whole stack, not just the visible top. Before moving anything, note where each colour is buried. A colour sitting at the bottom of three different tubes is the real obstacle on the board.
- Consolidate into one home tube per colour. When a colour appears on top of two tubes, always move onto whichever tube already holds more of it. Two half-finished tubes of the same colour cost you a slot you will need later.
- Watch the move cost of unstacking. A tube holding three identical balls takes three moves and three free slots to break apart, so prefer to unstack singles and pairs first.
- When two tubes block each other and every legal move just shuffles balls back and forth, stop and undo to the branch point instead of continuing.
About this puzzle
Ball Sort belongs to the same wave of mobile colour-sorting puzzles that spread across app stores around 2019 and 2020, and like the rest of that genre it has no verified single inventor or invention date.
Ball-in-tube versions appeared alongside liquid versions and later reskins using nuts, hoops and pins, all sharing one mechanic under different art.
The underlying problem - restacking items between a limited number of columns until each column is uniform - is a long-studied one in computer science, closely related to container-relocation problems.
A 2022 research paper, Sorting Balls and Water, formalised both variants, proved them equivalent in solvability, and showed the general problem is NP-complete.
Frequently asked questions
The rules are effectively the same; the difference is that balls move one at a time while liquid pours an entire run of matching units in a single action. A 2022 study proved the two are equivalent in solvability - any position solvable one way is solvable the other - so Ball Sort simply takes more taps to reach the same result.
There is no losing condition, so a stuck board just means no useful move remains. Undo back to where the position was still open, or restart the level, which is free.
The level as generated is solvable, but your own moves can ruin it - dropping a ball onto the wrong tube can bury a colour with no free slot left to dig it out. Undo is the only way back once that happens.
An empty tube is the only destination that accepts a colour that matches nothing else on the board. With zero empty tubes and no matching tops, the position is frozen regardless of how many balls are visible.
Standard Ball Sort has no clock and no move limit, so you can study the board as long as you like. The difficulty comes entirely from planning order, not from speed.
