Sextile

Sextile is astrology software for the keyboard. The interface runs in the terminal, the calculation underneath uses the Swiss Ephemeris, and the data stay as files on disk. A chart does not disappear into an account, a database on someone else’s server, or a format only the application itself can still open.

What matters is not only that a horoscope is calculated. It is what remains after the calculation. Sextile records the derivation: which factors were used, in which order they were applied, and which input would have to change for the result to change as well. The same input produces the same output and the same path there.

That places Sextile near the question of how much of a tool’s visible mechanism must stay exposed before a result can be inspected rather than merely consumed. Astrological software is useful material for this because its rules are numerous enough not to be trivial, but concrete enough that every step has to be named.

The open technical point is the derivation itself. At its current size, it remains readable. That proves little. Once more rules, exceptions, and interpretive layers are added, the project may lose the property that justifies it in the first place: a path that is not only stored correctly, but can still be followed by a human being.