Track your reading: search for books, log progress by page, percent, or listening time, and keep notes on every book in one place.
Live hand-drawn animations of 2D mechanisms (four-bar, slider-crank, gears, cam, pendulum, spring) from a simple code block.
Spreadsheet-style calculator that propagates measurement uncertainty: input forms, significant figures, expanded uncertainty, uncertainty budgets, and Monte Carlo, following the GUM and its Supplement 1.