Problem Statement

A magic square is an   N×N  square matrix whose numbers consist of consecutive numbers arranged so that the sum of each row and column,   and   both diagonals are equal to the same sum   (which is called the magic number or magic constant).
A magic square of doubly even order has a size that is a multiple of four   (e.g.     4, 8, 12). This means that the subsquares also have an even size, which plays a role in the construction.

Create a magic square of   8 × 8.

Let's start with the solution:

masksq=: >:@#@, | _1&^ * 1 + i.@$
pat4=: ,:(+.|.)=i.4
mask=: ,/@(,./"3@$&pat4)@] ,~ % 4:
demsq=: masksq@mask