Clutter is an open source software library for creating fast, visually rich and animated graphical user interfaces.

Clutter uses OpenGL (and optionally OpenGL ES for use on Mobile and embedded platforms) for rendering but with an API which hides the underlying GL complexity from the developer. The Clutter API is intended to be easy to use, efficient and flexible.

Many people, when first finding out about Google Web Toolkit, wonder "why can't I use Python instead of Java?". pyjamas is designed to make that possible.