projects (such as birthday cards and messages of appreciation) are intended to cultivate relationships. Others are designed to raise awareness on social issues (such as global warming and animal abuse). During the 2008 U.S. presidential election, a flurry of projects featured Barack Obama and John McCain and later a series of projects promoted members of the Scratch online community for the not-quite-defined position of “President of Scratch.”

Some Scratch projects grow out of school activities. For an Earth-science class, a 13-year-old boy from India created a project in which an animated character travels to the center of the Earth, with a voice-over describing the different layers along the way. As part of a social-studies class, a 14-year-old boy from New Jersey created a simulation of life on the island of Rapa Nui, designed to help others learn about the local culture and economy.

As Scratchers work on personally meaningful projects, we find they are ready and eager to learn important mathematical and computational concepts related to their projects (see Figure 5). Consider Raul, a 13-year-old boy who used Scratch to program an interactive game in his after-school center. 9 He created the graphics and basic actions for the game but didn’t know how to keep score. So when a researcher on our team visited the center, Raul asked him for help. The researcher showed Raul how to create a variable in Scratch, and Raul immediately saw how he could use it for keeping score. He began playing with the blocks for incrementing variables, then reached out and shook the researcher’s hand, saying “Thank you, thank you, thank you.” The researcher wondered how many eighth-grade algebra teachers get thanked by their students for teaching them about variables?

more social

Development of the Scratch programming language is tightly coupled with development of the Scratch Web site. 12 For Scratch to succeed, the language needs to be linked to a community where people can support, collaborate, and critique one another and build on one another’s work. 1

The concept of sharing is built into the Scratch user interface, with a prom-

three core design
principles for
scratch: make it
more tinkerable,
more meaningful,
and more social
than other
programming
environments.

inent “Share” menu and icon at the top of the screen. Click the Share icon and your project is uploaded to the Scratch Web site (see Figure 6) where it is displayed at the top of the page, along with the “Newest Projects.” Once a project is on the Web site, anyone can run it in a browser (using a Java-based player), comment on it, vote for it (by clicking the “Love It?” button), or download it to view and revise the scripts. (All projects shared on the site are covered by Creative Commons license.)

In the 27 months following the Scratch launch, more than 500,000 projects were shared on the Scratch Web site. For many Scratchers, the opportunity to put their projects in front of a large audience—and receive feedback and advice from other Scratchers—is strong motivation. The large library of projects on the site also serves as inspiration. By exploring projects there, Scratchers get ideas for new projects and learn new programming techniques. Marvin Minsky once said that Logo had a great grammar but not much literature. 11 Whereas young writers are often inspired by reading great works of literature, there was no analogous library of great Logo projects to inspire young programmers. The Scratch Web site is the beginning of a “literature” for Scratch.

The site is also fertile ground for collaboration. Community members are constantly borrowing, adapting, and building on one another’s ideas, images, and programs. Over 15% of the projects there are remixes of other projects on the site. For example, there are dozens of versions of the game Tetris, as Scratchers continue to add new features and try to improve gameplay. There are also dozens of dress-up-doll projects, petitions, and contests, all adapted from previous Scratch projects.

At first, some Scratchers were upset when their projects were remixed, complaining that others were “stealing” from them. That led to discussions on the Web site’s forums about the value of sharing and the ideas behind open source communities. Our goal is to create a culture in which Scratchers feel proud, not upset, when their projects are adapted and remixed by others. We have continually added new features to the site to support and encourage this mind-set. Now, when someone remixes