Foldline

Foldline is a self-contained geometric puzzle built around reflection across a line. Each study begins with a paper-like sheet containing printed marks. Draw a crease with the pointer, then choose which side of that crease should fold. Marks on the chosen side are reflected mathematically across the crease. The objective is to bring every mark to the same point within the fold budget shown for that study. Version 1.0.0 contains twelve curated studies covering vertical, horizontal, diagonal, offset, and multi-fold arrangements. The game includes undo, reset, a temporary crease hint, a study selector, persistent completion progress, and an unfold replay after a solved study. Geometry is calculated locally in JavaScript; there is no server-side puzzle validation or remote level feed. Foldline stores only the current study number and the identifiers of completed studies in the extension page's localStorage. It does not read webpages, browser history, tab URLs, or user documents. The toolbar action opens the packaged app.html page in a new tab. The background service worker performs no browsing-data inspection.