If you like to write out in public at a coffee shop, restaurant, or bar, then this is a writing prompt game you might enjoy. I guess it could work if your home has a window or balcony overlooking a public area – just make sure you have a decent number of people to work with.
How does it work? It’s simple. Pick a person or group of people you can see from your seat and make up a story about why they’re there and what they’re doing.
It’s really people-watching with a super-imposed storyline. It’s fairly simple, and I know plenty of people who aren’t writers who like to do it for casual amusement. My coworkers like to watch first dates and decide whether they’re going well or crashing and burning. Since you never know what people are actually going to do, your little story can be unexpectedly derailed as you’re writing it (we talk about our characters doing unexpected things, but in this case, it can really happen).
That doesn’t mean you have to match what they’re doing. You’re making up a story, not narrating real life. You can make them do whatever you want (cue evil laughter).