Normal sudoku rules apply. Each circle marks the head of a familiar line constraint which takes the form of a snake of length from 2 – 9 cells. The specific constraint is indicated by the colour of the circle (and by a letter on the colourblind friendly version). The circle contains the length of the snake. The snakes move orthogonally through the centres of some cells, and do not touch themselves orthogonally. Snakes may freely touch each other, but do not share cells. The grey cells in box 4 are not part of any snake. The featured clue types are as follows: Renban (purple/R): The digits on a renban line form a sequence of consecutive digits in any order; Region Sum Lines (Blue/ S): The cells along a region sum line in each 3x3 box it passes through sum to the same total. Region sum lines always occupy at least two regions; German Whispers (Green/W): Adjacent digits along a German whispers line differ by at least 5; Modular Lines (Yellow/M): Each string of three adjacent cells along a modular line contains one of 147, one of 258, and one of 369. Length two modular lines contain one of each of two of these groups; Entropic Lines (Orange/E): Each string of three adjacent cells along an entropic line contains one of 123, one of 456, and one of 789. Length two entropic lines contain one of each of two of these groups; Parity Lines (Red/P): Adjacent digits along a parity line have opposite parity; Ten Lines (Gray/T): Digits along a ten line must be entirely divided into non-overlapping groups of adjacent cells which sum to 10. Digits may repeat within these sums if allowed by other rules.