我怎样才能将事件发送到我的（子）UIView？

I'm new to Swift and have a hard time understand the event flow. The code below can be run directly in an xcode playground. I have a white UIView in the background. This view has a brown button and a red view as sub-views. Click on them and the events are logged in the controller, just as expected. I'm new to Swift and have a hard time understan