characters,

http, and

animations that build upon the core Dart and
Flutter libraries. Some of these packages come from the broader ecosystem,
covering services like

in-app
payments,

Apple
authentication, and

animations.

The rest of this overview broadly navigates down the layers, starting with the
reactive paradigm of UI development. Then, we describe how widgets are composed
together and converted into objects that can be rendered as part of an
application. We describe how Flutter interoperates with other code at a platform
level, before giving a brief summary of how Flutter’s web support differs from
other targets.

Anatomy of an app