group() {
	render(convexity = 1);
	render(convexity = 1);
	group() {
		difference() {
			cube(size = [100, 100, 100], center = true);
			multmatrix([[1, 0, 0, -50], [0, 1, 0, -50], [0, 0, 1, 0], [0, 0, 0, 1]]) {
				multmatrix([[-1, 0, 0, 0], [0, -1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
					group() {
						difference() {
							cube(size = [20, 20, 150], center = true);
							multmatrix([[1, 0, 0, -10], [0, 1, 0, -10], [0, 0, 1, 0], [0, 0, 0, 1]]) {
								cylinder($fn = 0, $fa = 12, $fs = 2, h = 80, r1 = 10, r2 = 10, center = true);
							}
						}
					}
				}
			}
			multmatrix([[1, 0, 0, 50], [0, 1, 0, -50], [0, 0, 1, 0], [0, 0, 0, 1]]) {
				multmatrix([[0, 1, 0, 0], [-1, 0, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
					group() {
						difference() {
							cube(size = [20, 20, 150], center = true);
							multmatrix([[1, 0, 0, -10], [0, 1, 0, -10], [0, 0, 1, 0], [0, 0, 0, 1]]) {
								cylinder($fn = 0, $fa = 12, $fs = 2, h = 80, r1 = 10, r2 = 10, center = true);
							}
						}
					}
				}
			}
		}
	}
	multmatrix([[1, 0, 0, 110], [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
		group() {
			difference() {
				cube(size = [100, 100, 100], center = true);
				multmatrix([[1, 0, 0, -50], [0, 1, 0, -50], [0, 0, 1, 0], [0, 0, 0, 1]]) {
					multmatrix([[-1, 0, 0, 0], [0, -1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
						group() {
							render(convexity = 2) {
								group() {
									difference() {
										cube(size = [20, 20, 150], center = true);
										multmatrix([[1, 0, 0, -10], [0, 1, 0, -10], [0, 0, 1, 0], [0, 0, 0, 1]]) {
											cylinder($fn = 0, $fa = 12, $fs = 2, h = 80, r1 = 10, r2 = 10, center = true);
										}
									}
								}
							}
						}
					}
				}
				multmatrix([[1, 0, 0, 50], [0, 1, 0, -50], [0, 0, 1, 0], [0, 0, 0, 1]]) {
					multmatrix([[0, 1, 0, 0], [-1, 0, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
						group() {
							render(convexity = 2) {
								group() {
									difference() {
										cube(size = [20, 20, 150], center = true);
										multmatrix([[1, 0, 0, -10], [0, 1, 0, -10], [0, 0, 1, 0], [0, 0, 0, 1]]) {
											cylinder($fn = 0, $fa = 12, $fs = 2, h = 80, r1 = 10, r2 = 10, center = true);
										}
									}
								}
							}
						}
					}
				}
			}
		}
	}
	multmatrix([[1, 0, 0, -110], [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
		difference() {
			render(convexity = 2) {
				difference() {
					cube(size = [100, 100, 100], center = true);
					cylinder($fn = 0, $fa = 12, $fs = 2, h = 110, r1 = 30, r2 = 30, center = true);
				}
			}
			multmatrix([[1, 0, 0, -55], [0, 1, 0, -55], [0, 0, 1, 45], [0, 0, 0, 1]]) {
				cube(size = [10, 10, 10], center = false);
			}
		}
	}
}