// A cylinder that matches cube()
module cylinder2(dim) {
  translate([0, dim[1]/2, dim[2]/2])
    rotate(90, [0, 1, 0])
    cylinder(dim[0], dim[1]/2, dim[2]/2);
}

module rcube(dim, r=3) {
  hull() {
    for (x = [r, dim[0]-r]) {
      for (y = [r, dim[1]-r]) {
	translate([x, y, 0])
	  cylinder(dim[2], r, r);
      }
    }
  }
}

module rbox(dim, wall=3, r=10) {
  w = dim[0];
  d = dim[1];
  h = dim[2];

  difference() {
    rcube(dim, r);
    translate([wall, wall, wall])
      rcube(dim - [wall*2, wall*2, 0], r);
  }
}

function midx(a, b) = (a[0] - b[0])/2;