[rawbot]

Maybe the rest of HN has a similar, better option, but I could recommend LEGO Mindstorms. Eleven would be a good age to start getting curious about robots and automation. You should of course, help her with it, as it may be too complex for her to handle alone at the start.

It is pricey new, but you could get an older version used for cheaper.

There's also Nintendo Labo, for a similar, less expensive version.

[n4bz0r]

Not quite the same thing, but, speaking of expensive parts. This post seems like the place to share the findings.

As a kid, I would absolutely love to have some of the Lego(-compatible) motors [0] that are now available on the Chinese market for a few bucks a piece.

Some of the 'regular' sets [1] look quite tempting, too. In the bang for the buck department, at least.

[0] https://aliexpress.com/item/1005004221490793.html

[1] https://aliexpress.com/item/1005003548518388.html

[ArnoVW]

LEGO Mindstorms is great, but it's amazingly expensive.

They recently released LEGO Boost, which has some limitations wrt Mindstorms, but you won't notice it unless you're doing advanced stuff. Moreover, it has a great app. And it's one third of the price of Mindstorms.

[cben]

Due to price, when you buy motors/sensors/hubs, you'd want them to be compatible with future buys. LEGO used to have several systems but now pretty much converged to one "Powered Up" interface: https://brickarchitect.com/powered-up/.

The app is indeed neat & powerful. Performance is limited by official firmware being "dumb", it reports sensor values and takes commands, all computations actually run in the app. However, what's cool is an essentially unbrickable bluetooth bootloader letting you try alternative FOSS firmware — see https://pybricks.com/.