Normal sudoku rules apply except that the regions are irregular. Additionally, a snake has to be drawn into the grid. The head and tail of the snake are in the two cells with the grey circles. The snake may not touch itself orthogonally, but it can touch itself diagonally. The clues outside the grid indicate the sum of the digits located on the snake. Considering "Snake" and "non-snake" as two colors, the given digits show how many cells orthogonally connected to the given are of a different color to the color of the given cell itself. All such possible digits are shown. Givens can be on or off the snake.