  Most of the 700 million teenagers everywhere in the world already have their
own smartphones, but comparatively few 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 versions of our free apps
since 2014 and 47 releases of the main coding app as of July 2018, Catrobat
currently has more than 700,000 users from 180 countries, is available in 50+
languages, and has been developed so far by almost 1,000 volunteers from around
the world ("the world"). Catrobat is strongly inspired by Scratch and indeed
allows to import most Scratch projects, thus giving access to more than 30
million projects on our users' phones as of July 2018. Our apps are very
intuitive ("rock bottom"), have many accessibility settings, e.g., for kids
with visual or cognitive impairments, and there are tons 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 Pi boards, going up to the
stratosphere and even beyond to interplanetary space ("the sky"). A
TurtleStitch extension allowing to code one's own embroidery patterns for
clothes is currently being developed. Catrobat among 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 is
discovered by our users through various app stores such as Google Play and via
social media channels such as YouTube as well as via our presence on Code.org.
