Divide the grid into pentominos (orthogonally connected 5-cell regions). Cells on either side of a given border must belong to different pentominos. Two pentominos of the same shape (including rotations and reflections) cannot share an edge.
Divide the grid into pentominos (orthogonally connected 5-cell regions). Cells on either side of a given border must belong to different pentominos. Two pentominos of the same shape (including rotations and reflections) cannot share an edge.