Normal sudoku rules apply. Draw a snake which starts at a grey circle and ends at the other grey circle, and never passes through a grey square. The snake moves orthogonally and/or diagonally and can cross itself and acts as a slow thermometer i.e. reading from one end to the other, digits on the snake increase or stay the same (the direction must be determined by the solver). Furthermore, the snake passes through at least 27 cells. The sum of the digits within a cage must sum to the small clue in the top-left corner of that cage.