Ball Sort

How to play

Tap a tube to pick it up, then tap another to move into it. Tap the same tube again, or press Escape, to put it down.

You can move onto a matching ball or into an empty tube, and nothing else. A refused move costs you nothing.

U takes a move back and R puts it forward. H shows one move worth making.

Rules and controls — Zerdly's preset

This game has two rules and the preset picks one. These are the rules Zerdly plays by:

• Every tube holds the same number of balls.
• Only the ball on top of a tube can move. A buried ball cannot go anywhere until the ones above it have left.
• You may move into an empty tube, or onto a tube whose top ball matches what you are moving.
• Starter, Classic and Expert move one ball at a time. This is the default and the rule most people expect.
• Run move takes the whole matching run at the top — or as much of it as fits. You never choose the amount. It is a separate preset because it is a different puzzle, not a harder one.
• A tube is sorted when it is full of one style. Uniform but not full does not count.
• A sorted tube gets a lid, and is still a legal source. You can move balls back out of it, and sometimes you have to.
• Empty tubes are fine, and are the room you have to work in. The puzzle ends when every tube is either empty or full of one style.
• Undo and redo are available in every preset.

Presets

• Starter — Four styles and two spare tubes, one ball at a time. Enough room to experiment, and short enough to finish in a minute.
• Classic — Six styles in the same two spare tubes. One ball moves at a time, so any stack can be taken apart — if you have somewhere to put it.
• Expert — Eight styles in deeper tubes. A tube holds five, so the stacks are taller and there is further to unpick.
• Run move — The other rule: a move takes the whole matching run at the top, not one ball. You cannot split a stack, so what you commit to matters more than where you put it.
• Daily Sort — One puzzle a day, the same for everybody, built from the date.

Tips

• Keep a spare tube genuinely empty for as long as you can. An empty tube accepts anything; a tube with one ball in it accepts one style.
• Look at what is UNDER the top ball before you commit. The patterns are there so you can, and the buried balls decide what your next three moves can be.
• Finish a style completely rather than half-collecting several. Every sealed tube is a tube that stops getting in the way.
• In Run move, count the run before you move. A run of three into a tube with room for two leaves one behind, and that leftover is what turns a tidy board into a stuck one.
• If you are stuck, undo rather than restarting — the position two moves ago is usually the one that went wrong, and a hint from there will tell you why.

Privacy and local play

Everything runs in your browser. Your current puzzle, your settings and your best times are kept on this device only, and the button under the board clears them without touching any other Zerdly tool. No account, no sign-in, and nothing about your play leaves the machine you are on.

Questions

How many balls move when I tap a tube?

It depends on the preset, and this is the one thing worth knowing before you start. Starter, Classic and Expert move exactly one ball — the one on top. Run move takes the whole run of matching balls at the top, or as much of it as fits. The status row above the board always says which rule is in force, because the two are genuinely different puzzles rather than the same one at different speeds.

Why is Run move a separate preset rather than a difficulty?

Because it changes what you are allowed to do, not how much of it there is. Moving one ball at a time means any stack can be taken apart, so the question is whether you have somewhere to put the pieces. Taking the whole run means you cannot split a stack at all, so the question is what you commit to. Same board, same balls, different game.

Can I still move balls out of a tube that is finished?

Yes, and sometimes you have to. A tube that fills up with one style gets a lid so it reads as done and stops competing for your attention, but that is a label rather than a rule — it stays a tube you can take balls back out of. On a tight board that is occasionally the only move available.

Can every puzzle actually be finished?

Yes, and not because of an argument — because each one was solved before it was handed to you. The board is built by mixing a finished set of tubes backwards, and that on its own does NOT guarantee anything: the move that would undo a mix is not always legal, so some reverse-mixed boards have no way home. About one board in a hundred, at the shapes shipped here. So every candidate goes through the solver, and anything that cannot be finished is thrown away rather than shown to you.

Why is a tube not finished when it looks finished?

A tube counts as sorted only when it is completely full of one style. Three matching balls with a gap above them means the fourth is somewhere else, and the puzzle will not end until it comes home. Empty tubes are fine — they are the room you have to work in.

Why does every ball have a pattern on it?

Because the colours are not enough on their own, and we measured that rather than assuming it. The eight styles were checked under three kinds of colour blindness, and at least one pair cannot be reliably told apart by hue. So each style carries its own marking, on every ball rather than just the top one — reading what is buried under the top is most of the game. You can switch the patterns off if you prefer, and the game will still work; it will just be relying on colour to tell you things.

Does a hint ever send me the wrong way?

No. It is worked out from the position you are looking at right now, not from where the puzzle started, so undoing a few moves and asking again gives you an answer about where you actually are. It tells you which kind of answer it found: a move on a shortest route home where the search can prove one, or a move on a route that finishes where it can only promise that.

Why does Expert have deeper tubes rather than fewer spare ones?

Because taking a spare tube away does not make the puzzle harder, it makes it impossible. On eight styles with one spare, only about nine boards in a hundred can be finished at all — so a preset built that way would spend its time rejecting puzzles rather than making hard ones. Expert adds styles and a fifth ball of depth instead, which means taller stacks and further to unpick.

How does the Daily work?

One puzzle a day, the same for everybody, built from the UTC date rather than your local one — so it changes at the same moment everywhere rather than at your local midnight. It always plays the Classic one-ball rule on the same shape, so a run of results means something. It is regenerated from the date rather than stored, which is why the generator version is part of the key.

Is anything sent to a server?

No. The puzzles, the solver, the hints, the sounds and your progress all run in your browser. There is no account, and clearing this game's data leaves every other Zerdly tool untouched.

Related interactives

• Colour Sort — the same furniture, liquids instead of balls, and a pour you never choose the size of.
• Number Link — connect the pairs and fill every square.
• Tangram Studio — fit seven pieces into a silhouette.
• Maze Labyrinth — find the way through, or ask for the thread.