RAT RUN 4: Borderline

Normal sudoku rules apply: place the digits 1-9 once each in every row, column, and 3x3 box (marked with dotted lines.)

AIM OF EXPERIMENT: Finkz the rat must reach the cupcake by finding a path through the maze (the path will be a snaking line that passes through the centres of cells, without visiting any cell more than once, crossing itself or passing through any thick maze walls.) Diagonal moves are not possible in this maze.

BLACKCURRANTS: Cells connected by a blackcurrant have a 1:2 ratio (one is double the other.) Not all possible blackcurrants have been given.

ONE-WAY DOORS: Finkz may only pass directly through a purple arrow if moving in the direction the arrow is pointing. An arrow always points to the smaller of the two digits it sits between.

TEST CONSTRAINT: In this experiment, the correct path will be a valid Region Sum line - ie: box borders (dotted lines) will divide the path into segments which each have the same sum.