Logic Masters Deutschland e.V.

Apologies for the long ruleset, but hopefully it's fairly intuitive.

Rules

Fill the grid so that each row, column and 3x3 box contains the digits 1-9 once each.

Shade some cells in the grid to be the 'crossnumber puzzle'. This puzzle must be a single orthogonally-connected region of the grid. The crossnumber puzzle must match the list of clues given below.

More precisely, any multi-cell horizontal or vertical run of cells in the crossnumber puzzle which reaches the edge of the puzzle in either side is an answer in the grid. These answers are numbered in the typical crossword fashion, i.e. with a number in its topmost/leftmost cell, which start at 1 and increment with each subsequent numbered cell in reading order through the whole sudoku (left-to-right then top-to-bottom). If a horizontal answer and a vertical answer have the same numbered cell, they are given the same number.

Each answer in the grid corresponds with a clue in the list (and vice versa) matching its number and whether it is across (horizontal) or down (vertical). The non-empty clues must accurately describe their corresponding answer, with e.g. "10a" in a clue referring to the answer for 10a, and "10" in a clue referring to the integer 10.

In addition, whenever a cell in the crossnumber puzzle is orthogonally adjacent to a cell outside the puzzle, the cell outside the puzzle contains the larger digit of the two.

Link

Play online here. NB: The starting grid is meant to be entirely blank.

Clues