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A larger board, the same rules
Seven rows, columns and regions require seven koalas.
Figure 1: begin with the single-square regions.
1. Place the three single-square regions
They are row 2 column 6, row 5 column 1, and row 7 column 2. Double-tap each, excluding its row, column, region and neighbors after every placement.
Figure 2: a certain starting point creates certain exclusions.
After all three, row 1 has only columns 3 and 4 available. Do not pick one at random.
2. Both candidates belong to the same region
Row 1 needs a koala. Both remaining candidates belong to the same large region, so that region’s koala must be in row 1. Its other remaining candidates, row 3 column 4 and row 4 column 5, are therefore excluded.
This is valid whichever of the two row-1 squares is ultimately correct.
Figure 3: a row’s candidate pair locks the region to that row.
3. Row 3 now has one candidate
Row 3 had columns 3 and 4 remaining. The region deduction removed column 4, leaving row 3 column 3. Place it.
Column 3 is now occupied, so row 1 loses its column-3 candidate. Place row 1 column 4.
4. Complete the remaining rows
Row 4 had columns 4 and 7 available. Column 4 is occupied, leaving row 4 column 7. The only unused row and column are then row 6 and column 5.
The final columns from top to bottom are 4, 6, 3, 7, 1, 5, 2. Check each region once and check that koalas in consecutive rows differ by more than one column.
Use what the candidates share
Two candidates do not force a guess. Look for a shared row, column or region, then ask what is excluded regardless of which candidate wins.
Review the 5×5 basics, or continue with 9×9 region deductions.