An Accessible Blocks Language: Work in Progress
Varsha Koushik, Clayton Lewis · 2016 · Proceedings of the 18th International ACM SIGACCESS Conference on Computers and Accessibility (ASSETS '16) · doi:10.1145/2982142.2982150
Summary
This demonstration paper presents Pseudospatial Blocks (PB), a nonvisual blocks programming language designed to make block-based coding environments accessible to blind learners. Block languages like Scratch, Snap, MIT App Inventor, and Microsoft Block Editor are among the most popular platforms for introducing children to programming, using visual shape cues (tabs and sockets) to show how program elements can be combined — eliminating the need to master complex textual syntax. However, these environments are completely inaccessible to blind users because they rely on graphical presentation of code and drag-and-drop mouse interactions. Several parallel efforts exist: Google's Accessible Blockly presents blocks as HTML structures readable by screen readers; Stephanie Ludi has proposed a Blockly-based approach supporting both visual and screen reader access; Bootstrap is extending its system for screen reader support; and tangible physical blocks projects (CubeCoding, Primo, Project Bloks) aim at coding by touch. PB takes a different approach inspired by T.V. Raman's principle that nonvisual presentations should be created as content that works well in themselves, rather than trying to make visual representations accessible through a screen reader.
Key findings
PB introduces the concept of "pseudospatiality" — a navigation scheme that uses arrow key navigation in a virtual two-dimensional space where the geometry is distorted but still navigable. The toolbox of available blocks is positioned to the "left" of the workspace, with blocks arranged "vertically" in both areas. A step "left" from any block in the workspace always reaches the same location in the toolbox, regardless of the block's vertical position — a geometric distortion that simplifies navigation. The key innovation replacing visual shape cues is syntactic category filtering: rather than showing which blocks can physically fit together through visual shapes, PB filters available program elements to show only those that are syntactically valid at the current cursor position. This provides the same error-prevention benefit as visual shape cues without requiring vision. The authors reference research by Schiff and colleagues showing that people navigating virtual environments with geometric or topological distortions experience no greater difficulty than in realistic ones, supporting the conjecture that PB's spatial distortions will not impair usability.
Relevance
This work addresses a critical equity gap in computing education: blind children are excluded from the most widely used introductory programming tools at exactly the age when programming concepts are most commonly introduced. As CS education becomes increasingly standard in K-12 curricula, this exclusion risks compounding disadvantages for blind learners. For accessibility practitioners, PB's approach offers a design lesson: rather than retrofitting visual interfaces for screen reader access (which often produces awkward experiences), designing natively nonvisual interactions that preserve the conceptual benefits of the visual approach (in this case, syntax error prevention through shape/category constraints) can yield more effective results. The syntactic filtering concept — showing only valid options at each point — is potentially applicable beyond programming to any structured editing task where users with visual impairments need to construct valid combinations of elements.
Tags: blindness · programming education · screen reader · education · STEM accessibility · inclusive design · software accessibility