group() {
	hull();
	hull();
	hull() {
		cylinder($fn = 0, $fa = 12, $fs = 2, h = 1, r1 = 10, r2 = 10, center = false);
		multmatrix([[1, 0, 0, 0], [0, 1, 0, 0], [0, 0, 1, 10], [0, 0, 0, 1]]) {
			cube(size = [5, 5, 5], center = true);
		}
	}
	multmatrix([[1, 0, 0, 25], [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
		hull() {
			multmatrix([[1, 0, 0, 0], [0, 1, 0, 0], [0, 0, 1, 10], [0, 0, 0, 1]]) {
				cylinder($fn = 0, $fa = 12, $fs = 2, h = 1, r1 = 3, r2 = 3, center = false);
			}
			difference() {
				cylinder($fn = 0, $fa = 12, $fs = 2, h = 4, r1 = 10, r2 = 10, center = true);
				cylinder($fn = 0, $fa = 12, $fs = 2, h = 5, r1 = 5, r2 = 5, center = true);
			}
		}
	}
	multmatrix([[1, 0, 0, -5], [0, 1, 0, -5], [0, 0, 1, -5], [0, 0, 0, 1]]) {
		hull() {
			intersection() {
				cube(size = [1, 1, 1], center = false);
				multmatrix([[1, 0, 0, -1], [0, 1, 0, -1], [0, 0, 1, -1], [0, 0, 0, 1]]) {
					cube(size = [1, 1, 1], center = false);
				}
			}
		}
	}
	group() {
		hull() {
			cube(size = [0, 0, 0], center = false);
			sphere($fn = 0, $fa = 12, $fs = 2, r = 0);
		}
	}
}