Water Sort: How to Sort Every Tube

The pouring rule

• You can pour into a tube that is empty, or whose top colour matches the colour you are pouring, as long as it has room.
• The whole top colour runs across, as many layers as fit. A tube holds four layers. If only one layer fits, one layer goes and the rest stays behind.
• Each pour is one move. Undo is free and does not count.

Every colour also carries its own symbol, a circle, a star, a heart and so on, so two shades that look alike can always be told apart. You can switch the symbols off in Options if you prefer plain colours.

Empty tubes are your working space

Think of the two empty tubes as the only free space on a workbench. Everything you do either uses that space or frees it again. Two kinds of pour use it up:

• Pouring into an empty tube turns free space into a stack you will have to finish or move again.
• Pouring onto a matching colour uses no free space at all. It is almost always the better move.

So the first question before every pour is: can this colour go onto a matching top instead of into an empty tube? If yes, do that.

A good order of moves

1. Free pours first. Look for a colour that sits on top of two different tubes. Pour one onto the other. Nothing is lost, and one tube now shows a new colour on top.
2. Finish what is nearly finished. A tube with three layers of one colour needs just one more. Find that colour on top somewhere and pour it in.
3. Dig for buried colours. When a colour you need is under one other layer, move that layer somewhere useful and the colour underneath comes free.
4. Use an empty tube for the colour you can complete soonest. Before you pour into an empty tube, count how many layers of that colour are on tops or just under one layer. If you can collect all four soon, the tube will be closed quickly and its space was well spent.

Mistakes to avoid

• Filling both empty tubes with half-stacks. With no empty tube left and no matching tops, you can be stuck. Undo, and try a pour onto a matching colour instead.
• Splitting a colour you already gathered. Pouring two red layers into a tube with room for only one leaves a red behind and makes two half-stacks out of one.
• Moving a finished colour. A tube with all four layers of one colour is done; the game will not let you ruin it, but moving three layers of one colour about is usually wasted too.
• Pouring a single-colour tube into an empty tube. It changes nothing but the move count.

The extra tube

Once a game you can add an extra empty tube. It costs five moves, which on the leaderboard is a lot, so treat it as a rescue rather than a tool. If you find yourself stuck, try Undo a few pours back first: most dead ends come from one early pour into an empty tube that should have gone onto a matching top.

Difficulty, scoring and the leaderboard

Every puzzle has two empty tubes, and every one has been checked by a computer solver, which sorted it with those two tubes alone before it was used. Water Sort is ranked by moves first, then by time; the extra tube adds five moves. Only a member's first solve of the day counts.

A routine for clean solves

1. Scan every top colour and note the ones that appear twice.
2. Make all the free pours onto matching tops.
3. Pick the colour closest to complete and plan its four layers.
4. Only then spend an empty tube, on that colour.
5. Repeat, and every time a tube gets its cork, check what its last pour uncovered.