Twine 2, Harlowe

{
(set: $alpha to false)
(if: $alpha)[The quick brown fox jumped over the lazy dog.]\
(if: $alpha is false)[The lazy dog failed to jump over the quick fox.\

[Give the dog a rest]<rest_dog|
(click-replace: ?rest_dog)[You gave the dog a rest.(set: $alpha to true)]]\
}