module rcube(size=[10, 15, 20], bbottom=3, btop=3) {
  module side(w, d, bevel) {
    tiny = 0.001;
    if (bevel == 0) {
      translate([0, 0, 0])
	cube(tiny);
      translate([w-tiny, 0, 0])
	cube(tiny);
      translate([0, d-tiny, 0])
	cube(tiny);
      translate([w-tiny, d-tiny, 0])
	cube(tiny);
    } else {
      translate([0+bevel, 0+bevel, 0])
	sphere(bevel);
      translate([w-bevel, 0+bevel, 0])
	sphere(bevel);
      translate([0+bevel, d-bevel, 0])
	sphere(bevel);
      translate([w-bevel, d-bevel, 0])
	sphere(bevel);
    }
  }

  hull() {
    translate([0, 0, bbottom])
      side(size[0], size[1], bbottom);
    translate([0, 0, size[2]-btop])
      side(size[0], size[1], btop);
  }
}