Summary:
Yin Yang (also called Shirokuro) is a two-colour logic puzzle where you fill a grid with light and dark circles so that each colour forms one connected group and no 2×2 block is all one colour. This tutorial explains the goal, the three rules, and how to make your first forced moves.
Overview
In a Yin Yang puzzle every cell holds a circle that is either light (an open ring) or dark (a filled disc). A few circles are printed as clues; you fill in the rest. There are three rules — one for each colour’s connectivity, and one banning solid 2×2 blocks — and every puzzle has exactly one solution you can reach by pure logic.
The puzzle as printed: the circles shown are the clues, and every blank cell is yours to fill.
The Goal
Fill every empty cell with one circle — light or dark — so the finished grid obeys all three rules below. When you are done, every cell holds a circle and there are no blanks left.
The Rules
A finished grid must satisfy all three:
- Light circles connect. Every light circle is joined to every other light circle in one single group, moving only up, down, left, or right (not diagonally).
- Dark circles connect. Every dark circle is likewise joined into one single group.
- No 2×2 is one colour. No block of four cells in a 2×2 square may be all light or all dark.
That is the whole puzzle: two colours, each in one connected piece, with no solid 2×2 patch of either. The light and dark groups end up interlocking, which is where the name comes from.
The Clues
- The printed circles are givens — your solution must keep them exactly as shown.
- A light clue is drawn as an open ring; a dark clue is a filled disc; an empty cell is left blank. So a light clue always looks different from a cell you still have to fill.
- The clues are placed so the rest of the grid is forced — there is exactly one way to finish the board.
How to Start Solving
Work from the rules; no board ever needs a guess. Start with these forced moves, using the puzzle pictured above.
1. Complete a 2×2. If three cells of a 2×2 square are already the same colour, the fourth must be the other colour, or you would break rule 3. This is the most common opening move, and there is one waiting on the board above: take the 2×2 block where the third and fourth rows meet the second and third columns. Three of those four cells are already dark, so the fourth — third row, second column — must be light. Fill it in and look for the next one.
2. Keep a group’s escape route open. Each colour must end up in a single group, so a group that gets sealed off by the other colour can never join the rest. The cue to look for: a group of one colour has only one empty cell still touching it, and there are more of that colour elsewhere on the board. That empty cell must be that colour — anything else strands the group.
3. Work the edges and corners. Border cells have three neighbours and corners only two, so they run out of escape routes first. A corner circle that can reach the rest of its colour through only one cell forces that cell.
4. Re-check both colours after every move. Every light circle must still have a path to the other lights, and every dark to the other darks. If a move leaves a single circle with no way out, it was wrong — undo it and take the other colour.
5. On Expert only, test and reject. Pick an undecided cell, assume it is light, and follow the forced consequences. If that leads to a broken rule, the cell must be dark. This one extra move is what separates Expert from the other three levels.
Moves 1 to 4 solve Easy, Medium and Hard boards outright. Repeat them until every cell is filled and all three rules hold — because the solution is unique, there is never a moment where two different colours would both work.
The same board finished: every cell filled, both colours in one connected group each, and no solid 2×2 anywhere.
When the Puzzle Is Not Drawn as Circles
Some Yin Yang books swap the rings and discs for something else: two colours, two letters, two numbers, or two little pictures. Puzzle Maker Pro can print any of those, so you may meet the same board looking like this:
The identical puzzle, printed with two colours. The clue positions are the same as the first image.
Nothing about the puzzle changes. There are still exactly two states, one plays the part of light and the other of dark, and all three rules apply unchanged. Everything in the solving section above works as written — just read the two symbols as colour A and colour B.
Difficulty (and why there is no guessing)
Every Puzzle Maker Pro Yin Yang puzzle has exactly one solution and is solvable by logic alone — no trial and error. What the difficulty setting changes is how much work the logic is:
- Easy fills about half the grid with clues, so forced moves sit next to each other and each one is short.
- Medium cuts that to a bit over a third, so you start chaining two or three deductions together.
- Hard strips the clues back as far as the connectivity rule allows. The moves are the same as on Medium, but the chains run much longer before a cell is forced.
- Expert is barely sparser than Hard — the difference is not the clue count but the thinking. It is the only level that needs move 5, the test-and-reject look-ahead. Choose it for solvers who are already comfortable with the other three.
Yin Yang is quick to teach and slow to exhaust: two colours and three rules, but the connectivity rule makes it genuinely deductive rather than pattern-filling. Most 8×8 boards take a few minutes once the two forced-move patterns are familiar.
Solving on Screen
Yin Yang is not only a paper puzzle. Puzzle Maker Pro can export a puzzle as a fillable PDF, where each blank cell is a text box you type your answer into while the printed clues stay locked, and as interactive slides, where you drag light and dark tiles onto the board. Puzzles published to the web are played by clicking a cell to cycle it through empty, light, and dark, with a check button that tells you whether the board is right and a live highlight on any solid 2×2 you create. The connectivity rule is checked when you press verify rather than as you type, because a half-finished grid is disconnected by definition.
Outcome
You now know the goal, the three rules, how the clues are drawn, and five forced moves that solve any board the generator produces. Ready to make your own? See How to Create Yin Yang Puzzles in Puzzle Maker Pro.
FAQ
Do diagonal connections count?
No. Circles join only up, down, left, or right. Two same-colour circles touching at a corner are not connected to each other.
Can a Yin Yang puzzle have more than one solution?
Not one made in Puzzle Maker Pro. The clues are placed so the rest of the grid is forced, giving exactly one solution you can reach by pure logic.
Is Yin Yang the same puzzle as Shirokuro?
Yes. They are two names for the same two-colour connectivity puzzle, and the rules are identical.
I am stuck and nothing seems forced. What now?
Re-check every 2×2 that already has three of one colour, then look for a group with only one empty cell touching it. If the board is Expert, you may need the test-and-reject move: assume a colour, follow it, and take the opposite if it breaks a rule.
What if the puzzle uses colours, letters or pictures instead of circles?
It solves identically. There are still two states, one standing in for light and one for dark, and all three rules apply unchanged.
How is Expert different from Hard?
Not by clue count — the two are almost equally sparse. Expert is the only level that requires the look-ahead move, where you assume a colour for one cell and reject it because it breaks a rule.