Rock bottom, the world, the sky: Catrobat, an extremely large-scale and long-term visual coding project relying purely on smartphones

Reference Format: Luhana, K., Mueller, M., Schindler, C., Slany,  W.,  Spieler, B. (2018) Rock bottom, the world, the sky: Catrobat, an extremely large-scale and long-term visual coding project relying purely on smartphones. In Proceedings of Constructionism 2018, 20. – 25. August, 2018, Vilnius, Lithuania.

Kirshan Kumar Luhana, Matthias Mueller, Christian Schindler, Wolfgang Slany, Bernadette Spieler
Institute of Software Technology, Graz University of Technology, Austria


Most of the 700 million teenagers everywhere in the world already have their  own smartphones, but comparativelyfew of them have access to PCs, laptops, OLPCs, Chromebooks, or tablets. The free open source non-profit project Catrobat allows users to create and publish their own apps using only their smartphones. Initiated in 2010, with first public versionsof our free appssince 2014 and47releases of the main coding app as of July 2018, Catrobatcurrently has more than 700,000 users from180 countries,is available in 50+ languages, and has been developed so far by almost1,000 volunteers from around the world(“the world”).

Catrobatis strongly inspired by Scratchand indeed allows to import most Scratch projects, thus giving access to more than 30million projects on our users’ phones as of July 2018. Our apps arevery intuitive(“rock bottom”), have manyaccessibility settings, e.g., for kids with visual or cognitive impairments, and there aretons of constructionist tutorials and courses in many languages. We also have created a plethora of extensions, e.g., for various educational robots, including Lego Mindstorms and flying Parrot quadcopters (“the sky”), as well as for controlling arbitrary external devices through Arduino or Raspberry Piboards, going up to the stratosphere and even beyond to interplanetary space (“the sky”). A TurtleStitch extension allowing to codeone’s own embroidery patterns for clothes is currently being developed. Catrobatamong others intensely focuses on including female teenagers. While a dedicated version for schools is being developed, our apps are meant to be primarily used outside of class rooms, anywhere and in particular outdoors (“rock bottom”, “the world”). Catrobat isdiscovered by our users through various app stores such as Google Play and via social media channels such as YouTubeas well as via our presence on Sharing,remixing, and collaborationis actively encouragedand supported. Catrobathas a very long term perspective in that it is independent of continuous funding and actively developed in a test-driven wayby hundreds of pro-bono volunteers from around the world. Our aim is to grow by a factor of thousand and reach a billion users by 2030. We warmly welcome new contributors in every imaginable field and way with open arms. Please join us and contact me via wolfgang@catrobat.orgtoday!

Keywords: Pocket Code, Game Design, Gaming, Gender Inclusion, Coding, Mobile Learning, Social Inclusion, Constructionism, Girls, Teenagers, Apps, Smartphones, Tinkering