[rich_harris]

I'll try — I'm currently fielding a zillion messages so excuse brevity!

Basically, you can only modify state _where it's declared_. If you want to allow the 'outside world' to modify that state, you need to expose a function that does so. This is unlike cases where you're passing around an observable object where anyone with a reference, which they need for reading, can also write to it by doing `thing.value += 1`.

This is something Solid gets right — you can only change a signal's value if you have a reference to its setter.

[troupo]

> fielding a zillion messages

Surely you mean signals? :)