  We present Aptly, an extension of the MIT App Inventor platform enabling
mobile app development via natural language powered by code-generating large
language models (LLMs). Aptly complements App Inventor's block language with a
text language designed to allow visual code generation via text-based LLMs. We
detail the technical aspects of how the Aptly server integrates LLMs with a
realtime collaboration function to facilitate the automated creation and
editing of mobile apps given user instructions. The paper concludes with
insights from a study of a pilot implementation involving high school students,
which examines Aptly's practicality and user experience. The findings
underscore Aptly's potential as a tool that democratizes app development and
fosters technological creativity.
