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Can You Solve This Puzzle Without Guessing?

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Try the puzzle

Rounded coral, yellow, mint, blue, and lavender Yodoku tiles surround a glowing golden light on a dark plum background

I started Yodoku with the idea of a simplified Sudoku: keep the row, column and region logic, and use lanterns instead of digits. Try this little garden before opening the walkthrough.

An empty four-by-four Yodoku puzzle. Row 1: yellow B, red A, red A, green C. Row 2: yellow B, yellow B, yellow B, green C. Row 3: yellow B, green C, green C, green C. Row 4: yellow B, blue D, green C, green C.
A real 4×4 Yodoku garden. Numbers identify rows and columns; letters identify colors.
Board description

Four rows and four columns. A is red, B yellow, C green, and D blue. Each letter identifies one connected color region.

  1. Row 1: B, A, A, C.
  2. Row 2: B, B, B, C.
  3. Row 3: B, C, C, C.
  4. Row 4: B, D, C, C.

The rules

  • Place exactly one lantern in each color.
  • Place exactly one lantern in each row and each column.
  • Lanterns cannot touch, even diagonally.

You’ll place four lanterns in total. Letters identify the color regions, and an X can help you keep track of squares you’ve ruled out.

Take a moment with the board. Which square gives you a certain start?

Just a hint

Find the color that occupies only one square. Then look at the row immediately above it.

Familiar logic, different clues

Classic Sudoku asks you to place each digit once in every row, column and box. Yodoku asks for just one lantern in each row, column and colored region, with one extra constraint: lanterns cannot touch. The question becomes which squares can still hold a lantern.

Minesweeper offers another useful comparison. Its numbers count neighboring mines, helping you eliminate possibilities. In Yodoku, a placed lantern rules out the squares around it. Marking those squares with Xs makes the next deduction easier to see.

If you’ve played Meowdoku or Zoodoku, the row, column and colored-region constraints will feel familiar. Those games place animals; here, you’re lighting a garden.

This small board has one solution. Try to explain your next placement before you make it; the walkthrough follows the logic one lantern at a time.

Read the solution walkthrough

One lantern opens the board

1. Start with the blue square.

Blue D has just one square: row 4, column 2. Every color needs a lantern, so that square must have one.

2. Look one row up.

The blue lantern rules out the first three squares in row 3: one directly above it and two touching it diagonally.

Row 3’s lantern must go in its only remaining square: row 3, column 4.

The blue lantern at row 4, column 2 rules out the first three squares in row 3. The remaining square at row 3, column 4 is highlighted.

3. Return to the two red squares.

Red A has two squares in the top row. Blue already uses column 2, so red must go at row 1, column 3.

4. Fill the last row and column.

Row 2 and column 1 are the last without a lantern. They meet at the yellow square at row 2, column 1.

The completed puzzle, with lanterns at row 1 column 3, row 2 column 1, row 3 column 4, and row 4 column 2.

Four lanterns: one in every color, row, and column, with none touching.

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