# Product ## Platform web ## Users The admin shares a link with people they are building or deepening friendships with — typically in person or via SMS. The visitor is someone the admin already knows and has contact with. They visit once to discover their signs and how they connect with the admin, then may send the result back via their own phone's messaging app. ## Product Purpose A private, single-page zodiac compatibility tool. A visitor enters their birthday (and optionally their first name) and instantly receives their Western Sun sign, Chinese zodiac animal + element + heavenly stem, and a personalized compatibility report comparing their signs to the admin's fixed profile (Virgo + Fire Dragon). No accounts, no tracking, no stored data. ## Positioning Combined Western and Chinese astrology in one tool. Most compatibility calculators offer one system or the other. This site gives both side by side — Western element/modality/ruling planet alongside Chinese animal, heavenly stem, and Wu Xing (Five Elements) dynamics — producing a richer, more nuanced friendship reading than either tradition alone. ## Operating Context Shared in person or via SMS. By the time someone is on the site, the admin and visitor already have each other's contact information. After viewing their chart, the visitor taps a button that opens their phone's native SMS app with a pre-filled link to the admin. No server-side SMS infrastructure — the visitor's own device sends the message. ## Capabilities and Constraints - Western Sun sign computation with element, modality, ruling planet - Chinese zodiac computation (Lunar New Year boundary-aware, 1900-2100) - Full compatibility engine: 12 Western signs x 12 Chinese animals x 5 elements, all rated vs. Virgo + Fire Dragon - Wu Xing (Five Elements) generating/controlling cycle analysis - Six Harming Groups (Liu Hai) detection for Chinese signs - Share tokens are self-attested base64url-encoded reports in the URL (no server storage, no database) - Fully static deployment — no server runtime, no API routes - SMS sharing via empty-recipient `sms:` URI (visitor's phone picks recipient; no phone number embedded in page source) - No analytics, no cookies with PII, no persistent storage - Admin birthday lives only in env vars, never in client bundle - English only; no localization planned ## Brand Commitments - Celestial, astrological, night-time visual identity - Stars, constellations, deep sky aesthetic - Dark background as the primary visual ground - Not tied to a commercial brand — a personal tool from the admin ## Evidence on Hand - Fixed admin profile: Virgo (Earth, Mutable, Mercury) + Fire Dragon (Yang Fire, 丙 / Bing) - Admin lucky numbers: 1, 6, 7 - Admin lucky colors: Gold, Silver, Gray - No testimonials, case studies, or press. Do not fabricate social proof. ## Product Principles 1. **Private by default.** The visitor's data never leaves their browser. The admin's data never leaves the server config. Nothing is stored. 2. **Two traditions, one reading.** Every report spans both Western and Chinese astrology — never one without the other. 3. **Personal, not commercial.** The site is a tool the admin shares with friends. No branding, no upsells, no accounts, no "sign up to see more." 4. **Calm and cosmic.** The visual experience should feel like looking at a star chart, not a SaaS dashboard. Quiet, dark, celestial. ## Accessibility & Inclusion - WCAG AA target — minimum 18px base font, 48px touch targets - No emojis in code, docs, or generated text - Dark mode only (consistent with night-sky aesthetic)