checkboard = surface_create(960, 640);
surface_set_target(checkboard);

color = 0;
xx = -32;
repeat 30
{
    xx += 32;
    yy = -32;
    color = !color;
    repeat 20
    {

        yy += 32;

        color = !color;

        if color = 0
            draw_set_color(c_black);
        else
            draw_set_color(c_white);


        draw_rectangle(xx, yy, xx+32, yy+32, 1);
    }
}