Nintendo's creativity is always at full force when it comes to Mario level design, but they have never made a tiny computer inside the game.
A new level created inside Super Mario Maker functions by the user 'Trousers,' logically named 'Run a Tiny Computer!' delivers the equivalent of a functioning calculator running inside the game. You can run a few simple sums by interacting with on-off gates that activate walking Bob-ombs, coins and P-switches to present the answer.
Of course, it's not possible to make a computer more complex than this. We're not looking at an Inception-esque scenario of a fully functioning console within a console here. The limits of Mario Maker are being pushed here, but the achievement here is big nonetheless. And who knows, this does suggest a bright future for level creation tools.
The course ID, if you want to play it, is 2DE4-0000-01b3-642b.