Tweak started back in 2001 when it became obvious that the eToy architecture in Squeak had hit the wall in terms of what the Morphic infrastructure could provide. Here is the original memo that started it all.
This is a project with a sprite creating a color wheel by using a color holder. The project itself can be found here: ColorWheel.prj.
The following project is from the book Powerful ideas in the Classroom and can be download here: RaceCars.prj
This is how a Tweak project looks: