Squeak includes a number of user interface frameworks:

1 An implementation of Morphic, Self’s graphical direct manipulation interface framework. This is Squeak’s main interface.

2 Tile-based, limited visual programming scripting in Etoys, based on Morphic.

3 A new, experimental interface called Tweak. In 2001, it became clear that the Etoy architecture in Squeak had reached its limits in what the Morphic interface infrastructure could do. Hewlett-Packard researcher Andreas Raab proposed defining a “script process” and providing a default scheduling mechanism that avoids several more general problems. The result was a new user interface, proposed to replace the Squeak Morphic user interface in the future. Tweak added mechanisms of islands, asynchronous messaging, players and costumes, language extensions, projects, and tile scripting. Its underlying object system is class-based, but to users, during programming (scripting), it acts like it is prototype-based. Tweak objects are created and run in Tweak project windows.

4 MVC, derived from the original Smalltalk-80 user interface framework which first introduced and popularized the Model-View-Controller architectural pattern[3] (so named after the three core classes of the framework). Thus, the term “MVC” in the context of Squeak refers to both one of the available user interface frameworks and the pattern the framework follows. MVC is provided for programmers who wish to use this older type of interface.