A sorting puzzle in disguise
Water Sort is a stack-sorting puzzle. Each tube is a stack where you can only reach the top. Each pour moves the top run of one colour onto a matching top, or into an empty tube. Every tube holds four units. Every colour has exactly four units, and every board deals two extra empty tubes. Those two empties are your entire working space, so the whole game is about using them well.
At the start, every coloured tube is full. That means your first pour must go into an empty tube. Nothing else has room. How you spend those first two empties shapes the rest of the game.
Spend the empties wisely
- Pour long runs into empties. If one tube has two or three units of the same colour on top, pouring it into an empty uses the space well. A single unit in an empty tube does little and takes a whole tube out of play.
- Free space, then use it. Every pour leaves room at the top of the tube you poured from. That gap is new working space. Look for another unit of the colour now on top elsewhere, and pour it there.
- Prefer pours that reveal a match. Before you pour, look at the colour under the run you're moving. If that colour is sitting on top of another tube, the next pour is already lined up. Pours that uncover a colour with no match tend to stall.
- Combine before you start fresh. If two tubes show the same colour on top, pour the smaller run onto the larger one. Use an empty tube only when no matching pour helps.
Here is a short example on Easy, with five colours in seven tubes. Say tube one has two reds on top with blue underneath. Tube three has a single blue on top. Pour the two reds into an empty tube. Tube one now shows blue, with two free spaces above it. Pour tube three's blue onto it. Tube three shows a new colour too, and tube one is building a run of blue. One empty tube has opened two useful pours.
Plan the finish
A tube is finished when it holds four units of one colour. It gets a cork. Aim to finish tubes early, because a corked tube is one less thing to track. Count as you go. If three units of green are already together, find where the fourth is buried and work toward it.
Watch the pour size too. A pour carries the whole top run, but only as much as fits. Pour three units onto a tube with one free space, and only one moves. The other two stay where they were. That is sometimes what you want, but often it splits a run you just built. Check the free space before you pour.
How players get stuck
The classic dead end is filling both empty tubes with mixed colours. When every tube is full, or every top colour is different, no pour is possible. Keep at least one empty tube, or one tube with a clear plan, for as long as you can.
Undo has no limit, so a dead end is never final. Step back to the last moment you still had an empty tube, and try a different pour there. Hint plays the next pour of a solution from where you are. If none exists, it says "No hint available", which tells you to undo a few pours. Hinted pours count as moves, and a hinted solve doesn't set your best.
From five colours to eight
Easy has five colours in seven tubes, Medium six in eight, and Hard eight in ten. Every level keeps exactly two empty tubes, so harder boards give you the same working space with more to sort. That is why the empty-tube habits matter more as you climb. Your best, the fewest moves, is saved for each difficulty. Once you can finish Easy without hints, replay it to lower your move count before moving up. Each unit also shows a small digit from 1 to 8, so similar shades are easy to tell apart.
