While this is too simple (even the website admits that a bot could be written in virtually no time to break it), it does make me wonder if you could have a WarioWare CAPCHA. A minigame with extremely vague description that you have to react to quickly to pass. Thinking about it some more it fails the primary criteria for a CAPCHA: it needs to be harder to write the bot that cracks it than each test case, by at least…
Which would have the side effect of putting the bot makers to work on useful and hard problems to solve.