Yup, we do an hour. After that, it feels like there's diminishing returns. There's absolutely no expectation anyone will "finish", and we make that clear. It's the journey we're interested in, not the destination.

One that we tend to do a lot is creating an image gallery using Flickr or Unsplashed's API. It's vague enough that people can take it in whatever direction they want, and simple enough that you can get pretty far in an hour.