Normal sudoku rules apply. The grid hides a labyrinth: a single continuous region of orthogonally connected cells. A 2×2 block may never consist entirely of labyrinth cells. There are no dead ends in the labyrinth (every labyrinth cell is connected to at least two other labyrinth cells). All remaining cells are walls. Walls form isolated groups of exactly four orthogonally connected cells. “Isolated” means that wall cells from different groups cannot touch each other, not even diagonally. Digits within a group of walls do not repeat and sum to 14. An X between two cells indicates that their digits sum to 10. ALL Xs ARE GIVEN. An X is always framed when it lies between two cells of the same type: either labyrinth cells or wall cells.