Miscellany
A spreadsheet and a slide deck that share one document — so a figure on a slide is the number in the sheet, not a copy of it.
Free and open source, MPL-2.0. No account, no install, no dependencies. Your file is read in the browser tab — the page makes no external requests at all.
Opens your Excel workbook, lets you work in it, and gives it back without wrecking it. Change one cell in a file full of pivot tables and macros we cannot even display, and every part we did not touch comes back byte-for-byte.
Slides whose numbers and charts are bound to cells. Edit the sheet and the bar grows, the axis rescales, the percentage recomputes — with no synchronisation code, because a slide object and a cell are the same kind of thing.
Both apps save to a single file that stores what you typed, never what was computed, one node per line so it diffs in Git. Nothing in the format can execute.