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Monodoku's Queens-style puzzle guide

Every move
has a reason.

Learn 10 logic techniques for Queens-style games, including Monodoku and Meowdoku. Practice on interactive Monodoku boards, from single openings to forced moves.

Explore the techniques

The basics / 01

What an animal rules out

Every animal takes up its row, column and color. Its neighbors are off limits too, including diagonals. Use Xs to keep track.

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A REAL MONODOKU POSITION4 × 4

Outlines show the reason. Rings show the next move.
Small numbers identify matching colors.

Step 1 of 6

This animal rules out its row, column, color, and touching squares. Mark those squares with Xs.

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  1. This animal rules out its row, column, color, and touching squares. Mark those squares with Xs.
  2. Mark the ringed squares with Xs.
  3. The Xs are in place. Now look at the remaining openings.
  4. Column 2 has only one square left.
  5. Place an animal in the ringed square.
  6. The monkey belongs in row 4, column 2.

The basics / 02

One opening in a color

Each color needs one animal. When only one square in that color is still available, you have your next placement.

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A REAL MONODOKU POSITION4 × 4

Outlines show the reason. Rings show the next move.
Small numbers identify matching colors.

Step 1 of 3

This color has only one square left.

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  1. This color has only one square left.
  2. Place an animal in the ringed square.
  3. The monkey belongs in row 2, column 1.

The basics / 03

One opening in a row

Scan across a row without an animal. If all but one square are ruled out, the remaining square must hold its animal.

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A REAL MONODOKU POSITION4 × 4

Outlines show the reason. Rings show the next move.
Small numbers identify matching colors.

Step 1 of 3

Row 3 has only one square left that can take a piece.

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  1. Row 3 has only one square left that can take a piece.
  2. Place an animal in the ringed square.
  3. The monkey belongs in row 3, column 4.

The basics / 04

One opening in a column

The same idea works vertically. A column with just one available square tells you exactly where to place an animal.

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A REAL MONODOKU POSITION4 × 4

Outlines show the reason. Rings show the next move.
Small numbers identify matching colors.

Step 1 of 3

Column 2 has only one square left.

Read the full explanation
  1. Column 2 has only one square left.
  2. Place an animal in the ringed square.
  3. The monkey belongs in row 4, column 2.

Reading the board / 05

A color owns a line

A color's openings can all lie in one row or column. You may not know the exact square yet, but you can rule out other colors in that line.

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A REAL MONODOKU POSITION4 × 4

Outlines show the reason. Rings show the next move.
Small numbers identify matching colors.

Step 1 of 7

This color needs one animal. The outlined squares are its remaining openings.

Read the full explanation
  1. This color needs one animal. The outlined squares are its remaining openings.
  2. Every opening is in column 1. This column is reserved for that color's animal.
  3. Other colors cannot use this column. Mark the ringed squares with Xs.
  4. The Xs are in place. Now look at the remaining openings.
  5. This color has only one square left.
  6. Place an animal in the ringed square.
  7. The monkey belongs in row 1, column 2.

Reading the board / 06

A line uses up a color

If every opening in a row or column belongs to one color, that line must use the color's animal. Cross out that color's openings elsewhere.

Open the full lesson
A REAL MONODOKU POSITION4 × 4

Outlines show the reason. Rings show the next move.
Small numbers identify matching colors.

Step 1 of 7

Row 2 needs one animal. The outlined squares are its remaining openings.

Read the full explanation
  1. Row 2 needs one animal. The outlined squares are its remaining openings.
  2. Every opening belongs to the same color. That color must place its animal in this row.
  3. That color cannot place another animal elsewhere. Mark its ringed squares with Xs.
  4. The Xs are in place. Now look at the remaining openings.
  5. Row 1 has only one square left that can take a piece.
  6. Place an animal in the ringed square.
  7. The monkey belongs in row 1, column 3.

Reading the board / 07

Colors share a set of lines

Two colors confined to two rows need both rows. Three colors in three columns need all three. Other colors cannot use those reserved lines.

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A REAL MONODOKU POSITION4 × 4

Outlines show the reason. Rings show the next move.
Small numbers identify matching colors.

Step 1 of 7

Each outlined color needs one animal. These 2 colors need 2 animals altogether.

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  1. Each outlined color needs one animal. These 2 colors need 2 animals altogether.
  2. All their openings are in columns 3, 4. Those 2 columns are reserved for these 2 animals.
  3. Other colors cannot use these columns. Mark the ringed squares with Xs.
  4. The Xs are in place. Now look at the remaining openings.
  5. This color has only one square left.
  6. Place an animal in the ringed square.
  7. The monkey belongs in row 4, column 2.

Thinking ahead / 08

A larger set of lines

Look for the same pattern across four or more colors. When those colors have exactly as many available lines as animals, the lines are reserved.

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A REAL MONODOKU POSITION6 × 6

Outlines show the reason. Rings show the next move.
Small numbers identify matching colors.

Step 1 of 7

Each outlined color needs one animal. These 4 colors need 4 animals altogether.

Read the full explanation
  1. Each outlined color needs one animal. These 4 colors need 4 animals altogether.
  2. All their openings are in columns 1, 4, 5, 6. Those 4 columns are reserved for these 4 animals.
  3. Other colors cannot use these columns. Mark the ringed squares with Xs.
  4. The Xs are in place. Now look at the remaining openings.
  5. Column 1 has only one square left.
  6. Place an animal in the ringed square.
  7. The monkey belongs in row 5, column 1.

Thinking ahead / 09

A square that cannot work

Imagine placing an animal in a candidate square. If that immediately leaves a row, column or color with no opening, the candidate must be an X.

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A REAL MONODOKU POSITION7 × 7

Outlines show the reason. Rings show the next move.
Small numbers identify matching colors.

Step 1 of 7

Imagine an animal in the square marked ?. This is only a test.

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  1. Imagine an animal in the square marked ?. This is only a test.
  2. Now column 4 has nowhere for its animal. Every column needs one, so our test cannot work.
  3. That test leads to an impossible board. The square marked ? must be an X.
  4. The Xs are in place. Now look at the remaining openings.
  5. This color has only one square left.
  6. Place an animal in the ringed square.
  7. The monkey belongs in row 5, column 2.

Thinking ahead / 10

Follow the forced moves

Sometimes a test placement forces another animal, then another. If those forced moves reach an impossible position, rule out the original square.

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A REAL MONODOKU POSITION8 × 8

Outlines show the reason. Rings show the next move.
Small numbers identify matching colors.

Step 1 of 8

Imagine an animal in the square marked ?. This is only a test.

Read the full explanation
  1. Imagine an animal in the square marked ?. This is only a test.
  2. Row 1 would have just one opening. Animal 1 would have to go here.
  3. Now column 2 has nowhere for its animal. Every column needs one, so our test cannot work.
  4. That test leads to an impossible board. The square marked ? must be an X.
  5. The Xs are in place. Now look at the remaining openings.
  6. Column 7 has only one square left.
  7. Place an animal in the ringed square.
  8. The monkey belongs in row 1, column 7.

Examples use the game's own hint engine. A test placement is temporary; only the proven move is applied.

You'll learn as you play

No need to memorize it all.

Begin with the basics. Monodoku introduces new techniques with a visual lesson when you need them. Hints explain the reasoning, one step at a time.

Try your first puzzle

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