group() {
	projection(cut = true, convexity = 0) {
		square(size = [1, 1], center = false);
	}
	projection(cut = true, convexity = 0) {
		multmatrix([[1, 0, 0, 20], [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
			cube(size = [10, 10, 10], center = true);
		}
	}
	multmatrix([[1, 0, 0, 0], [0, 1, 0, 20], [0, 0, 1, 0], [0, 0, 0, 1]]) {
		projection(cut = true, convexity = 0) {
			multmatrix([[1, 0, 0, 0], [0, 1, 0, 0], [0, 0, 1, -4.999999], [0, 0, 0, 1]]) {
				cube(size = [10, 10, 10], center = true);
			}
		}
	}
	multmatrix([[1, 0, 0, 0], [0, 1, 0, -10], [0, 0, 1, 0], [0, 0, 0, 1]]) {
		projection(cut = true, convexity = 0) {
			union() {
				difference() {
					cube(size = [5, 5, 5], center = true);
					cube(size = [4, 4, 4], center = true);
				}
				multmatrix([[1, 0, 0, 2.1], [0, 1, 0, 2.1], [0, 0, 1, 0], [0, 0, 0, 1]]) {
					difference() {
						cube(size = [5, 5, 5], center = true);
						cube(size = [4, 4, 4], center = true);
					}
				}
			}
		}
	}
	multmatrix([[1, 0, 0, -15], [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
		minkowski(convexity = 0) {
			projection(cut = true, convexity = 0) {
				difference() {
					cube(size = [10, 10, 10], center = true);
					cube(size = [5, 5, 20], center = true);
				}
			}
			square(size = [1, 1], center = false);
		}
	}
}