multmatrix([[1, 0, 0, -20], [0, 1, 0, 5], [0, 0, 1, 0], [0, 0, 0, 1]]) {
		group() {
			minkowski(convexity = 0) {
				difference() {
					square(size = [10, 10], center = true);
					square(size = [8, 8], center = true);
				}
				circle($fn = 0, $fa = 12, $fs = 2, r = 2);
			}
		}
	}
	multmatrix([[1, 0, 0, 0], [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
		group() {
			minkowski(convexity = 0) {
				difference() {
					square(size = [10, 10], center = false);
					square(size = [5, 5], center = false);
				}
				circle($fn = 0, $fa = 12, $fs = 2, r = 5);
			}
		}
	}
	multmatrix([[1, 0, 0, 25], [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
		group() {
			minkowski(convexity = 0) {
				square(size = [10, 10], center = false);
				circle($fn = 0, $fa = 12, $fs = 2, r = 5);
			}
		}
	}