Duodoku - Rules & Guide

Tip 1: Find breakthroughs from non-overlapping edges

Although overlapping areas make up the majority, non-overlapping edge areas (i.e., the L-shaped periphery limited only by a single disk surface) are often excellent entry points. Because the constraints of the edge grid are relatively few and intuitive, after the number is determined, the clue can be quickly "pushed" into the overlapping area.

Tip 2: Use misplaced grids for cross elimination

This is the core technique of ghosting Sudoku. Due to the misalignment and overlap of the two disks, a 3x3 grid on the solid-line disk often spans multiple grids on the dotted-line disk. When you determine a number in a certain square on the solid line disk, it not only excludes the relevant areas on the solid line disk, but can also use its physical position to perform powerful "cross-border exclusion" on the squares on the dotted line disk.

Tip 3: Merge two candidate data sets

In the overlapping area, each square has two identities at the same time (for example: it is row 2 of the black disk and row 1 of the blue disk). When you are considering candidates for a certain grid, be sure to intersect its restrictions on the black board with the restrictions on the blue board. This kind of double pressure can often directly help you squeeze out the only solution.

Example image: The depth of the solid line and the dotted line are overlapping

A: Counted as two Sudokus at the same time! The number you fill in the overlapping area must ensure that it does not violate the rules in the black solid line Sudoku, and it does not violate the rules in the blue dotted line Sudoku. It can be said to be "one fish, two meals".

A: Absolutely not. Since the overlapping area is very large (8x8), it is far from enough to look at any one disk alone with known conditions. They must be regarded as a whole, and the double constraints of mutual transmission and superimposition between the two can be used to solve the puzzle smoothly.