“Mystery Meat” refers to on-screen elements and features that are hidden until you click, tap or hover on them, or actions you have to perform without the help of on-screen guidance. Think right-clicking or tap-and-holding on an link in Safari to open it in a new tab ¹, or the pinch-and-zoom in iOS: until you learn about it, you don’t know it exists.

The new iPhoto app for iOS, released with the new iPad, as beautiful as it is, is filled with mystery meat UI. Lukas Mathias at Ignore the Code summarizes his iPhoto experience:

Touching and gesturing in different ways would make seemingly random things happen. I regularly unintentionally activated features, changed views, opened or closed pictures, and got iPhoto into states I wasn’t sure how to get out of again.

He gives several examples where the UI is simply inscrutable to new users, including my favorite:

There’s some on-screen help, but it’s mostly useless. For example, Apple’s help tells you to «touch and hold with two fingers to use the magnifying loupe.» But once you do that, there’s no further help or information! The loupe seems to support different zoom levels. How do you access them? I don’t know. Are there other features the loupe supports? I don’t know. Can you access the help system again, to get additional information? Nope, trying to do that just closes the loupe.

After experimenting and figuring it out (two fingers on the edge and rotate, like focusing a camera lens), it was a cool feature, but how was anyone supposed to know this ahead of time? As Lukas concludes:

It’s okay to have a few gestures that aren’t easily discoverable, if they are simple, universally applicable, and fun enough that people will teach them to each other. Pinch-to-zoom is one such gesture. Most people probably won’t discover it on their own, but it’s such a fun gesture that the people who know it will show it to those who don’t. It’s also easy to learn and remember, and it works pretty much everywhere, so pinching pictures quickly becomes second nature.

Unfortunately, iPhoto’s hidden gestures aren’t particularly fun, and they only work in iPhoto.