Extra credit

🌟🌟🌟 Congratulations on getting this far! 🌟🌟🌟

If you still have some time here's a fun exercise you can try this:

People don’t stand still. What should happen if Sean shouts when he’s 1100m from Lucy and then shouts again when he’s 900m from Lucy? What should happen if Lucy is 1100m away from Sean when he shouts, but some time later she moves closer to him?

Once you have decided how Shouty should behave, write scenarios to drive out this behaviour.