> For the complete documentation index, see [llms.txt](https://android-course.cornellappdev.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://android-course.cornellappdev.com/chapters/2.-jetpack-compose.md).

# 2. Jetpack Compose

[Jetpack Compose](https://developer.android.com/jetpack/compose) is a modern toolkit designed to simplify UI development. It combines a reactive programming model with the conciseness and ease of use of the Kotlin programming language. It is fully declarative, meaning you describe your UI by calling a series of functions that transform data into a UI hierarchy. When the underlying data changes, the framework automatically re-executes these functions, updating the UI hierarchy for you.