function shiftZ(obj, delta) {
if (typeof obj.z != 'undefined') obj.z += delta
if (obj.parent) shiftZ(obj.parent, delta) // Set z recursively to parent
function shiftZ(obj, delta) {
if (typeof obj.z != 'undefined') obj.z += delta
if (obj.parent) shiftZ(obj.parent, delta) // Set z recursively to parent