Consecu-doku is a variant of classical Sudoku. It still involves rows, columns, and

mini-boxes and as usual, digits 1 through 9 must exist in all of them without conflict.

Unlike classical Sudoku, Consecu-doku grids contain circles between some adjacent

cells. Those circles indicate that the numbers in those cells must be consecutive

(ascending or descending).

Also, the numbers in adjacent cells that do not have a circle CANNOT be consecutive.

These puzzles can be solved using the typical Sudoku solving techniques (ie. hidden

singles, naked singles, hidden doubles, triples, etc). They can be solved without

resorting to advanced strategies such as X-wings, XY-Wings ,Swordfish, etc.

Here are a few tips to get you started:

Tip #1 Look at solved cells and "givens"

Cells adjacent to solved or given cells will eliminate candidates as shown here:

Tip #2 Look for cells with 2 circles

Cells with two circles on opposite sides cannot contain a 1 or a 9

The digit 1 can only be consecutive with digit 2. Since it is not possible to have

two 2's in the same row, digit 1 is not possible in the center cell. Similarly, digit

9 can only be consecutive with digit 8. So 1's and 9's are not possible in cells

with two opposite circles.

When a cell has two circles not opposite to each other ("L" shaped), these cells

also cannot be 1 or 9 if the cells reside in the same box).

In the example below, the three adjacent cells do not reside in the same box.

In this case 1's and 9's are still possible.

Tip #3 Look for cells that are missing 2's or 8's

When a cell is missing a 2, adjacent cells with circles

cannot contain a 1

Cells with missing 8's will remove 9's from adjacent cells with circles

Tip #3 Look for bivalue cells with consecutive values

Bivalue cell have only two candidates remaining. If they are consecutive,

they will eliminate those candidates from adjacent non-circled cells.

The pair in the center cell (45) are consecutive which allows removal of

those candidates from adjacent cells with no circles. Also note how the pair

affects the adjacent circle cell to the left. The candidates in that cell must be

within -1 below or +1 above the pair, otherwise they are eliminated.

Tip #4 Think "parity" (ie. even or odd)

Consecutive cells must have opposite parity. If all candidates in a cell are odd,

candidates in adjacent circled cells must be even (and vice versa)

Note how the candidates alternate between even and odd in the adjacent circled cells.

Tip #5 Look for hidden singles

A hidden single is found when a number exists in only one cell of a row, column, or box.

Candidate 8 exists only once in box 6. It causes multiple eliminations

as shown (it also solves the cell to the left which becomes a 9. Hidden

singles can be hard to spot but they will be frequent finds.