$fn = 200;
d = 200;

module main() {
  difference() {
    scale([1, 1, .5]) sphere(d = d);
    translate([d / -2, d / -2, 0]) cube([d, d, d]);
    translate([d / -2, d / -2, d * -1.2]) cube([d, d, d]);
    echo(d * .2);
  }
}

difference() {
  translate([-149, -149, 0]) cube([298, 298, 45]);
  rotate([180, 0, 0]) difference() {
    translate([-150, -150, -46]) cube([300, 300, 45]);
    translate([0, 0, 1]) scale([.95, .95, .95]) main();
  }
}