Logic Masters Deutschland e.V.

Draw two lines: one connecting the cells marked “A” and one connecting the cells marked “B”. The lines can only move orthogonally. Each cell can be visited only once and by only one line. Lines are not allowed to enter cells with a blue square or a yellow diamond.

Both lines are unique region sum lines: box borders will divide the line into segments which each have the same sum N. If a line passes through the same box more than once, each individual segment of such a line within that box sums to N separately. Each line segment must have a unique combination of digits. Different permutations of the same digits are not considered unique. Different lines can have different values of N.

Rotation switch: if you rotate the middle 3x3 box of the puzzle by 180 degrees, you should still have exactly two lines (i.e. no loose ends or isolated loops anywhere in the diagram). However, now both lines connect an “A” to a “B”. After rotation, the two lines are no longer valid unique region sum lines.

Blue squares: the digit in a blue square indicates the number of cells directly around it (orthogonally and diagonally) that are visited by a line before rotating the switch.

Yellow triangle: the digit in a yellow triangle indicates the number of cells in the direction of the arrow that are visited by a line.