Reachability in a Planar Subdivision with Direction Constraints — scientific demo
Copyright 2026 Pedro Machado Manhães de Castro.

Original implementation code is licensed under Apache License 2.0 (LICENSE).
Original explanatory text, diagrams and screenshots are licensed under Creative
Commons Attribution 4.0 International (https://creativecommons.org/licenses/by/4.0/).
These grants exclude third-party material and institutional marks.

Scientific source:
Daniel Binham, Pedro Machado Manhães de Castro, and Antoine Vigneron.
Reachability in a Planar Subdivision with Direction Constraints.
33rd International Symposium on Computational Geometry (SoCG 2017),
LIPIcs 77, Article 17, pages 17:1–17:15.
DOI: https://doi.org/10.4230/LIPIcs.SoCG.2017.17
The original article remains CC BY 3.0; its PDF and extracted research copy
retain the authors' attribution and original license. No original paper figure
is presented as newly authored demo material.

We would like to thank Daniel Binham and Antoine Vigneron.
Development assistance: OpenAI Codex. Interface revision 0.6 (layout,
interaction and its documentation) assisted by Anthropic Claude.

Copied presentation assets retain their own licenses. See public/licenses/ for
the license texts of KaTeX and fonts. Institutional and personal brand assets
were copied unchanged from Pedro's authorized reference site and are not
relicensed by this package.

Scientific scope: The literal Algorithm 1 skeleton trace from Section 4 is
preserved separately from an exact edge-interval closure extension. An audited
line-cone counterexample showed that the accepted semantics did not justify the
previous negative-result contract. Final negative certificates now require an
independently checked closure fixed point. The extension and its proof are
additional work, not attributed to the article authors or Theorem 1. No error
in the article is asserted. Neither stage is guaranteed to terminate. Algorithm
2's O(n log n) bound is not claimed. Rendering uses floating-point screen
coordinates; the exact scope and audit are documented separately.