The Arrow Rule

Arrow Sudoku is visually stunning and logically fascinating. It adds circles (bulbs) connected to arrows that wind through the grid.

The Rule: The digits placed along the path of an arrow must sum to the value placed in the bulb at the start of that arrow.

Combinatorics and Restrictions

Because the sum must fit into a single digit in the bulb, the sum cannot exceed 9. This means an arrow that is 4 cells long MUST contain the numbers 1, 2, 3, and 4 (which sum to 10... wait! That means an arrow cannot be 4 cells long if numbers can't repeat, but in Arrow Sudoku, numbers CAN repeat along the arrow as long as standard Sudoku rules aren't violated!).

If an arrow passes through a 3x3 block, the numbers inside that block cannot repeat, which severely restricts the available sums.