This is Tiny Kanban - the entire app from One app, seven renderers, inlined from the dependency-free vanilla keyed-patch implementation. Add a card, click a title to edit (Enter saves, Escape cancels, blur saves), move cards between columns, filter, reset - then refresh the page and note what persists. That behavior contract is everything each of the seven implementations had to reproduce. View source to read the whole app; the other six live in the repo.