/**
 * @return true if the array is null or has no elements.
 */
@OptIn(ExperimentalContracts::class)
fun <Type> GdxArray<Type>?.isEmpty(): Boolean {
  contract {
    returns(false) implies (this@isEmpty != nu

// before 0.10
box({
    // some styling DSL
}) {...}

// starting with 0.10. absolutly equivalent
div({
    // some styling DSL
}) {...}