Normal sudoku rules apply. Draw a path along the grey lines from the lower-left to the top-right that goes through all ⬡ cells. ⬡ cells indicate that the digits before and after them along the path have a 1:2 ratio. Red squares must be coloured depending on their odd/even parity. The path must separate the red cells such that all red cells in each region are the same colour. It is NOT REQUIRED that red cells in adjacent regions be of different colour.