1Presentation onlyYour logic is never touched.Script, data model, expressions, master items, variables, bookmarks and section access are never touched.
2Rehearsed on a copyYour app sees it last.Every change is proved on a copy, then replayed on your app after you sign off.
3Values gateEvery chart, every bookmark.Every chart identical under every agreed bookmark, with a test user per section access profile.
4Speed checkedMeasured, not assumed.Calc time for every sheet measured before and after, and reported. Measured and reported, never promised.
5One-command undoOff in one step.The whole glow-up comes off in one step, and your originals stay as Classic sheets throughout.
6Same app IDNothing breaks downstream.Links, bookmarks and community sheets keep working, because it's the same app.