Each of the 16 puzzles has a unique ruleset. Here are the rules for puzzle 1. You'll need to discover the rest of the puzzles' rules as you go! Normal 4x4 sudoku rules apply. The difference between a pair of adjacent digits along a coloured line equals the number of adjacent pairs along that line that have that difference. The black dot sits between two digits with a 1:2 ratio (ie one digit will be double the other).