Logic Masters Deutschland e.V.

Rules:

Normal Sudoku rules apply.

Shade some cells (walls) such that all shaded cells are connected orthogonally by other shaded cells to the edge of the grid, and the remaining unshaded cells (cave) form one orthogonally connected area. Note that 2x2 areas that are entirely shaded or entirely unshaded *are* allowed.

Digits in cells with circles cannot be shaded, and represent the total number of unshaded cells seen horizontally and vertically from that cell, including itself. Shaded cells block the vision.

Digits in cells with squares must be shaded, and represent the total number of connected shaded cells in the group that cell is a part of.

The unshaded cells (cave) act as a region sum line: 3x3 region borders divide the cave into segments that have an equal sum. If there are multiple unconnected cave sections within the same 3x3 region, those sections are summed separately.