Divide the grid into five regions, each containing 5 orthogonally connected cells. Place a digit from 1-5 in each cell so that digits do not repeat in a row, column or region. 'Marbles' join cells that share a region, and no two marbles share a region. Draw a 'Marble Run' from any cell in the top row to a 3 in a bottom corner. The marble run line is formed entirely of L-shaped line segments: a downwards movement (to gain speed) and then a horizontal movement of the same distance. Adjacent cells on the Marble Run are in different regions. Use the pentomino information provided around the grid to discover a secret code and enter it at the top of the grid to reveal the final rule.