Each row and column must contain the digits 1-9 exactly once, and there are nine orthogonally connected regions in the grid that also contain the digits 1-9. Each region takes the form of a “friendly serpent”, which is one cell wide, 9 cells long, and does not touch itself, even diagonally. Each serpent has a head and tail, also to be determined by the solver. Think of the head of the snake as its first cell, the next cell as the second, and so on. A cell in the grid is circled if the digit it contains matches its position in its snake. That is, the head is circled if it is a 1, and the tail is circled if it is a 9, and so on. ALL circles have been given.