Liquid Sort — free colour sorting puzzle, no download

Each tube holds four units of coloured liquid, jumbled together. Tap one tube and then another to pour, and the pour is allowed when the receiving tube is empty or already has the same colour on top, and has room. Every unit of that colour sitting on top pours across at once. Clear a level when every tube holds a single colour or nothing at all — then the next level arrives with one more colour to untangle.

The thing that makes this version fair is that every level is verified solvable before you see it. The game shuffles the liquid, then searches the position to confirm a solution exists, and deals it only if one does. You still have to find that solution — and you can still paint yourself into a corner, which is where the run ends. You get three undos for the whole run, so a corner is survivable but not free, and every level carries a pour budget of roughly double what a perfect solution needs. Free, no download, and a run in progress is saved if you close the tab.

How to play

• Tap a tube to lift its top colour, then tap another to pour.
• You can only pour onto the same colour, or into an empty tube.
• All the units of that colour on top move together — you cannot pour just one.
• Finish a level when every tube is one colour or empty. Your score is levels cleared.
• Three undos for the whole run, and each level has a pour budget — about double what a perfect solve needs. Spend it and the run ends.

Why the empty tube is the whole game

There are two spare tubes and they are not a convenience, they are your only working memory. Every difficult position in this puzzle is really the same problem: a colour you need is buried under a colour that has nowhere to go. An empty tube is the one place a stranded colour can be parked, so the moment you fill both spares with junk, the position stops being a puzzle and becomes a dead end.

That leads to one rule worth following almost blindly: never pour into an empty tube if any other legal pour exists. Pouring onto a matching colour costs you nothing and often frees the tube underneath; pouring into an empty tube spends your most valuable resource to move liquid that is still just as stuck as it was. When you must use a spare, use it on the colour with the most units already gathered elsewhere, because that is the one most likely to be reunited and emptied again quickly.

The budget is why flailing is expensive. Measured by exhaustive search, the shortest solution to a level runs at about three pours per colour — eight or so at three colours, twenty-four at eight — and you are given six per colour. That is roughly double the optimum, which is plenty for thinking and not nearly enough for guessing. Restarting a level gives you the same deal back but does not refund the pours you already spent.

The second habit is to look for chains before you start. A pour that unblocks a second pour that unblocks a third is worth far more than three unrelated tidy-ups, and unlike most puzzles here you can see the entire state at a glance — nothing is hidden, so a level you fail is a level you misplayed. If you enjoy that kind of full-information planning, Traffic Jam and Sokoban are the same shape of problem with blocks instead of colours.

More games

Another network to untangle: Pipes.

More puzzles with a guaranteed solution: Sokoban, Traffic Jam, Nonogram and Lights Out. Or browse all games.