Normal sudoku rules apply. Draw a snake that starts and ends at a purple spot and has a purple spot exactly at its centre. The snake can only move orthogonally from cell to cell, and may not touch itself, not even diagonally. The snake functions as a “zipper line” ie any pair of digits that are an equal distance from the central spot sum to the digit on that central spot. Any pair of cells connected by a clue (dot, diamond, X or V) must either both be on the snake, or both be off the snake. Cells connected by a white dot contain consecutive digits. Cells connected by black dot contain digits in a 1:2 ratio (ie one is double the other.) Cells connected by a green dot must contain digits with a difference of at least 5. Cells connected by a red diamond contain digits with the same parity (ie both are odd or both are even.) Cells connected by an X contain digits summing to 10. Cells connected by a V contain digits summing to 5.