module step(len, mod)
{
    for (i = [0:$children-1])
        translate([ len*(i - ($children-1)/2), 0, 0 ]) child((i+mod) % $children);
}

for (i = [1:4])
{
    translate([0, -250+i*100, 0]) step(100, i)
    {
        sphere(30);
        cube(60, true);
        cylinder(r = 30, h = 50, center = true);

        union() {
            cube(45, true);
            rotate([45, 0, 0]) cube(50, true);
            rotate([0, 45, 0]) cube(50, true);
            rotate([0, 0, 45]) cube(50, true);
        }
    }
}