Scratch is a visual programming environment that allows users (primarily ages 8 to 16) to learn computer programming while working on personally meaningful projects such as animated stories and games. A key design goal of Scratch is to support self-directed learning through tinkering and collaboration with peers. This article explores how the Scratch programming language and environment support this goal.

This paper presents an open source platform Throw [

Scratch is a networked, media-rich programming environment designed to enhance the development of technological fluency at after-school centers in economically-disadvantaged communities. Just as the LEGO MindStorms robotics kit added programmability to an activity deeply rooted in youth culture (building with LEGO bricks), Scratch adds programmability to the media-rich and network-based activities that are most popular among youth at after-school computer centers. Taking advantage of the extraordinary processing power of current computers, Scratch supports new programming paradigms and activities that were previously infeasible, making it better positioned to succeed than previous attempts to introduce programming to youth.Our working hypothesis is that, as kids work on personally meaningful Scratch projects such as animated stories, games, and interactive art, they will develop technological fluency, mathematical and problem solving skills, and a justifiable self-confidence that will serve them well in the wider spheres of their lives.

An incremental constraint solver, the DeltaBlue algorithm maintains an evolving solution to the constraint hierarchy as constraints are added and removed. DeltaBlue minimizes the cost of finding a new solution after each change by exploiting its knowledge of the last solution.