Robert Frost’s second poetry collection, Confounded.

Confounded shuffles up the words, and it’s up to you to put them right. It shows them to you in order—you just have to remember briefly and touch the words in sequence. Which is not always as easy as it seems.

But if it does seem too easy for you, the words can appear all at once, so you have to work out the sequence yourself. Still, it’s simply a matter of thinking like Robert Frost. Or memorizing the poem beforehand. (Or, perhaps, reading along with a book, though that would make it easier than ever.)

There are other variations too: change the display speed, have the words appear beat by beat instead of a whole word at a time, even not shuffle the words at all. And if you sometimes just want to watch the words go by, you can do that too.