# Features

What youros promises, part by part. Each promise is one sentence and why it
matters; a line off the left margin goes up to the story on
[Why](/why) it serves, and *proof* beside it opens onto what would show it,
the tests that name it and whether each passed.

<Parts />

## Reading a promise

A promise's slug (`files/moves`) is what code names with `meets:` and tests
with `proves:`, so what shows it is worked out from the code, never typed.
Hover a line in the margin for how the promise serves its story, and follow
it to land on the story. A promise nothing names yet says *not built*. How
each part keeps its promises is under [How it works](/how-it-works), and
every choice, with what it was chosen over, under
[Choices](/how-it-works/choices).