At the other end of the scale there's the aforementioned piano, which is utterly, utterly ingenious. Everything is made from cardboard, right down to the keys which use folded flaps to spring back into place when pressed. The Joy-Con slots into the back, with its IR camera pointed at a small slot just above the rear of the keys. When one is pressed, it pops into view through the slot and reveals small strip of reflective tape - the camera picks this up and plays the relevant note. The same visual trick is used to change the tone of the keyboard, adjust the pinch, record patterns and much more besides; you can even use the slot on the top of the piano to insert a cut-out (created by yourself) which changes the sound of a keypress based on the shape of cardboard.
The first time you witness this, it's nothing short of magic. You can't fathom how this primitive cardboard assembly is producing these sounds with such accuracy (despite the promotional video showing it quite clearly). Run your finger down the keys and it plays a perfect sequence of notes; turn the dial on the top-left and the tone of each note is subtly altered. Even when you realise the IR camera is behind all of this - perhaps the best application it's ever had, in fact - you'll struggle to withhold your amazement. It's jaw-dropping stuff, made all the more remarkable by the fact that Nintendo takes delight in lifting the curtain and showing how it's done; the app even presents you with a real-time read-out which shows the "hit boxes" the IR camera is looking for so you can place the reflective tape correctly. Even when fully constructed, the piano has an easy-to-access flap which allows you to open it up and view how it all works inside; there's a child-like joy in seeing these tricks revealed.