Celestium
An astrology app I designed and built end to end: the astronomical engine, the productized reading, the brand, and the funnel that sells it. This page is the debrief; the product itself lives on its own site.
What it is
Celestium is a cosmic compass for two questions most astrology apps skip: where to be, and when to act. It maps your birth chart onto the whole planet (astrocartography), reads the real transits touching your chart as seasons rather than a forecast, and can read your chart back to you in a voice your chart chooses. Everything computes on your device; no account, no tracking. It is live on the App Store for iPhone, iPad, and Mac.
What I built
The engine
A four-module Swift package (~103k lines): natal computation, transit synthesis, astrocartography, and more, validated against Swiss Ephemeris across 190 years. The accuracy is published, not asserted.
Engine case study →The product
A productized natal reading; depth encoded into archetypes so a real reading can scale, with the human-curated layer where it actually matters. Free 90-second voiced taste, paid full reading.
Product case study →The brand + funnel
Its own brand and marketing site, a signed-in account surface with identity tokens for MCP clients, App Store attribution, and a Substack. The whole path from a search to an install.
See it live ↗What it demonstrates
End-to-end product ownership. Not one slice; the whole stack. A real astronomical engine held to scientific standards, a product built on top of it, a brand that stands on its own, and the distribution to reach people. It is the clearest single answer to what I can build alone.
See the live product
The marketing site, the free voiced reading, and the download all live at celestium.me.