Tessella

Tessella is an editor for polygon tessellations of the plane: interactively create, view and manipulate tilings made of simple (regular and irregular) polygons.

Features:

* Add polygons from a palette, or by clicking any boundary edge, with automatic validation that keeps a proper edge-to-edge finite tessellation.
* Editing tools: eraser (vertices, edges, polygons), interior insertion, and "Add Copy" to grow a tiling by welding on a copy of itself under a plane isometry (translate, rotate, reflect, glide reflect), snapping to exact anchors.
* Selection and styling: select by click, colour or shape; recolour with a built-in colour picker.
* Pan, zoom and rotate the canvas; export to SVG and DOT.

The app is a thin WebView wrapper around the same client-side editor that is published on the web and as a PWA. Everything runs on-device: no network access, no accounts, no trackers.

A better uniformity overlay on incomplete patches.

* When a tiling is too small or too irregular for its exact symmetry classes to be defined, the overlay now colours vertices by the symmetry of the patch as drawn, instead of by a grouping that answered no clear question.
* A single polygon is now shown as the one class it obviously has.
* The summary now names which measure it used, so counts from different tilings are no longer confusable.