Normal sudoku rules apply. Cells must be shaded to form a single closed loop that is 1-cell wide. The loop may not touch itself, even diagonally. Within each cage, the sum of the shaded squares and the sum of the unshaded squares is equal. Digits must not repeat within a cage. The circles contain a digit equal to the number of adjacent cells that are part of the loop. This total includes the cell itself, the orthogonally adjacent squares, and the diagonally adjacent squares. Not all circles are given.