Irasuto

Irasuto (Illustration Configuration) is a logic puzzle. It requires you to fill in a grid, setting each cell to either white or black.

Rules: Colour the grey cells of the grid black or white. Cells with numbers must not be recoloured.
A number in a black (white) cell indicates the sum of all black (white) blank cells seen in total when looking north, south, east, and west (up to a different colored cell, a cell with a number, or the edge of the grid).