Blocks programming environments (BPEs) lower barriers to programming using visual code fragments that prevent syntactic and static semantic errors and reduce cognitive load. App Inventor, for example, provides a BPE that helps programmers of all levels to build mobile device apps easily. However, visual blocks notations can make programs more difficult to read, write, edit, and share. Dual-mode environments that allow bidirectional conversion between isomorphic blocks and text representations can leverage the benefits of both modes. Having recognized the advantages of allowing textual editing as a plug-in in BPEs, I have designed Venbrace, a fully-braced textual syntax isomorphic to the blocks-based programming language in App Inventor, based on a collection of design principles. I implemented a lexer, a parser, and a syntax editor for Venbrace. To ensure the usability of Venbrace, I also developed, conducted, and did a preliminary analysis of the first round of a user study (with 17 subjects) to evaluate its initial syntax design, determine some design choices, and explore possible improvements. This project aims to (1) increase App Inventors general usability, (2) maximize the usability of Venbrace through user studies, and (3) confirm the benefits of evidence-based programming language design. Keywords: App Inventor, Blocks Programming, Evidence-Based Programming Language Design, Human-Language Interaction (HLI)
