Logic Masters Deutschland e.V.

This puzzle uses both Japanese Sum and Cross the Streams logic to find 9 regions that are separated by shaded cells, and each contains every digit from 1 to 8.

The estimated difficulty of the puzzle should be a high 3 / low 4, based on testers' feedback and my intention to create an approachable puzzle using this ruleset before creating one using the digits from 1 to 9.

The rules to solve this puzzle are as follows:

1. Shade some of the cells and write a number from 1 to 8 in every unshaded cell such that no digit repeats within a row or column. Shaded cells cannot contain numbers. A row or column does not necessarily contain every digit from 1 to 8.

2. The shaded cells form a single orthogonally connected group. No 2×2 area within the grid can be totally shaded.

3. There are nine orthogonally connected sets of unshaded cells containing each digit from 1 to 8 exactly once. Each unshaded cell is part of such a region and the regions may not touch orthogonally but may touch diagonally.

4. The clues to the left side of the grid are Japanese Sum clues. A number indicates the sum of the digits in a consecutive set of unshaded cells. The clues are given in the right order. Each distinct clue is separated by at least one shaded cell.

5. The clues to the top of the grid are Cross the Streams clues. A number indicates the size of each group of consecutive shaded cells in that column, in order from top to bottom. Each distinct clue is separated by at least one unshaded cell.

6. A question mark (?) represents a single-digit number, and a double question mark (??) indicates a double-digit number. An asterisk (*) implies that any number of blocks may exist, including zero.

7. Each distinct letter represents some unique digit from 0 to 9.

You can play the puzzle online using the following link: Penpa+

The following example illustrates the rules using the numbers from 1 to 5 to construct 5 regions, and using 4 letter cipher (ABCD from 1-4):

Hope you have fun!