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Hard technique

Obvious Pairs (Naked Pairs), Explained

Most sudoku guides call these naked pairs. In Bubble Sudoku they are Obvious Pairs.

When two cells in a row, column, or block show the same two colors and nothing else, those colors belong to those two cells. Remove them from every other cell there.

1

Read the block

BEFORE

This block has six open cells. None of them shows a single color, so nothing can be placed yet. Look at the cells with the fewest dots.

2

Find the matching pair

The first two cells of the top row both show only Yellow and Dark Green. One will be Yellow and the other Dark Green. You do not need to know which.

3

Remove those two colors from the rest

Yellow and Dark Green are taken by the pair, so no other cell in the block can have them. Yellow comes off four cells. Dark Green comes off one.

4

Place what is left

AFTER

The top right cell had Yellow and Dark Blue. With Yellow gone, only Dark Blue is left. Place it. The Dark Blue dot in the bottom right comes off. The pair is still undecided, and that is fine.

Cells being readKey cellColor tints match the color being followed

Key Insight

Look at the cells with the fewest dots first. Two cells with the same two colors is the quickest pattern to spot. You never need to know which cell gets which color. Removing the two colors from the other cells usually reveals a new answer nearby.

Related Techniques

Obvious TriplesThe same idea with three cells and three colors.Hidden PairsThe same pattern found from the other side: two colors that can only go in the same two cells. It clears notes inside those two cells instead of around them.

If you’re stuck on a puzzle, see what to try next, in order.

Bubble Sudoku’s hints walk you through Obvious Pairs on a real board, one step at a time.

Try a Hard board

Also on iPhone and Android.