Build a Biorhythm App with Cursor and RoxyAPI in 30 Minutes

About the author: Torsten Brinkmann is an Astrologer and Developer Advocate with 16 years of experience in Western astrology and software engineering. He holds an M.Sc. in Computer Science from TU Munich and has contributed to open-source ephemeris and chart rendering libraries. His writing addresses both the astronomical mathematics behind calculations and the developer integration patterns for APIs.

The problem with building biorhythm features from scratch

You want to add biorhythm readings to your wellness app, productivity tool, or AI chatbot. You search for "biorhythm calculation" and find the sine wave formula. Simple enough: Math.sin(2 * Math.PI * daysSinceBirth / period). Three lines of code for the three primary cycles.

Then reality hits. Users want more than raw numbers. They want to know what a 74% physical cycle actually means. They want critical day warnings. They want the difference between "rising" and "peaking." They want interpretations in their language.

The formula is 5% of the work. The other 95% is phase detection (8 distinct states per cycle), editorial-quality interpretations, energy ratings, trend analysis, forecasting, compatibility scoring, and localization into 8 languages. Building all of that from scratch is weeks of domain research you should not be doing.

How the RoxyAPI Biorhythm API solves this

The Biorhythm API gives you 6 endpoints covering every biorhythm use case:

Every response includes editorial interpretations, not just numbers. Your UI gets structured data it can render directly. No NLP processing, no prompt engineering, no content writing.

Ready to build this? RoxyAPI Biorhythm API gives you 10 cycles, 8 languages, and editorial guidance out of the box. See pricing.

Step 1: Get your API key and install the SDK

Sign up at roxyapi.com/pricing and grab your API key from the dashboard. Then install the TypeScript SDK:

npm install @roxyapi/sdk

That is it. One package, full types, IDE autocomplete for every endpoint.

Step 2: Call the reading endpoint

The reading endpoint is your core building block. Send a birth date and target date, get back everything you need.

curl example:

curl -X POST https://roxyapi.com/api/v2/biorhythm/reading \
  -H "Content-Type: application/json" \
  -H "X-API-Key: YOUR_API_KEY" \
  -d '{"birthDate":"1990-07-15","targetDate":"2026-04-11"}'

TypeScript SDK:

import { RoxyAPI } from '@roxyapi/sdk';

const roxy = new RoxyAPI({ apiKey: process.env.ROXY_API_KEY });

const reading = await roxy.biorhythm.getReading({
  birthDate: '1990-07-15',
  targetDate: '2026-04-11',
});

console.log(reading.energyRating);   // 5
console.log(reading.overallPhase);   // "mixed"
console.log(reading.interpretation); // Editorial 3-5 sentence assessment
console.log(reading.advice);         // Actionable guidance for the day

Response structure (abbreviated):

{
  "birthDate": "1990-07-15",
  "targetDate": "2026-04-11",
  "daysSinceBirth": 13054,
  "energyRating": 5,
  "overallPhase": "mixed",
  "cycles": {
    "physical": {
      "value": -40,
      "phase": "falling",
      "phaseLabel": "Falling",
      "trend": "falling",
      "daysUntilPeak": 16,
      "daysUntilCritical": 10,
      "interpretation": "Your physical energy is declining..."
    },
    "emotional": { "value": 97, "phase": "peak", "trend": "peaking" },
    "intellectual": { "value": -46, "phase": "falling", "trend": "falling" },
    "intuitive": { "value": -16, "phase": "falling", "trend": "falling" },
    "aesthetic": { "value": -49, "phase": "falling", "trend": "falling" },
    "awareness": { "value": -26, "phase": "falling", "trend": "rising" },
    "spiritual": { "value": 95, "phase": "peak", "trend": "peaking" },
    "passion": { "value": 29, "phase": "rising", "trend": "falling" },
    "mastery": { "value": -43, "phase": "falling", "trend": "falling" },
    "wisdom": { "value": 26, "phase": "rising", "trend": "falling" }
  },
  "interpretation": "Your emotional sensitivity and creative energy are at their maximum...",
  "advice": "Engage in creative work and meaningful conversations today.",
  "criticalAlerts": []
}

Ten cycles. Phase detection. Trend analysis. Critical day warnings. Editorial text. One API call.

Step 3: Display results in your Cursor project

Open Cursor, create a new file, and let the AI assistant scaffold your UI. Paste this prompt into Cursor chat:

Build a biorhythm dashboard component that displays energy rating as a gauge, shows the three primary cycles (physical, emotional, intellectual) as progress bars from -100 to 100, and renders the interpretation and advice text below.

Cursor will generate the component. Feed it the response shape above and it will type everything correctly. The structured JSON maps directly to UI elements with zero transformation.

For a React component, the mapping is direct:

function BiorhythmDashboard({ reading }) {
  return (
    <div>
      <EnergyGauge rating={reading.energyRating} phase={reading.overallPhase} />
      <CycleBar label="Physical" value={reading.cycles.physical.value} />
      <CycleBar label="Emotional" value={reading.cycles.emotional.value} />
      <CycleBar label="Intellectual" value={reading.cycles.intellectual.value} />
      <p>{reading.interpretation}</p>
      <p>{reading.advice}</p>
    </div>
  );
}

No biorhythm math. No phase logic. No content writing. The API did all the work.

Step 4: Add daily readings for returning users

The daily endpoint is designed for "biorhythm of the day" features. Pass a user seed and get a consistent reading for that user on that date. Same seed plus same date always returns the same result, which is perfect for caching and push notifications.

curl example:

curl -X POST https://roxyapi.com/api/v2/biorhythm/daily \
  -H "Content-Type: application/json" \
  -H "X-API-Key: YOUR_API_KEY" \
  -d '{"seed":"user123","date":"2026-04-11"}'

TypeScript SDK:

const daily = await roxy.biorhythm.getDailyBiorhythm({
  seed: 'user123',
  date: '2026-04-11',
});

console.log(daily.energyRating);  // 6
console.log(daily.spotlight);     // Featured cycle with message
console.log(daily.dailyMessage);  // Concise daily summary
console.log(daily.quickRead);     // { physical, emotional, intellectual }

Response:

{
  "date": "2026-04-11",
  "seed": "user123-2026-04-11",
  "energyRating": 6,
  "overallPhase": "mixed",
  "spotlight": {
    "cycle": "emotional",
    "value": 72,
    "phase": "high",
    "message": "Your emotional awareness is heightened today..."
  },
  "quickRead": {
    "physical": 45,
    "emotional": 72,
    "intellectual": -30
  },
  "dailyMessage": "Your energy today is a 6/10...",
  "advice": "Lean into creative and social activities..."
}

The spotlight cycle rotates per user, creating variety across your user base while keeping each individual's experience consistent.

Step 5: Ship it in Cursor with vibe coding

Here is the full pattern. In Cursor, prompt the AI with your complete flow:

I am building a wellness app. Use the RoxyAPI SDK to fetch a biorhythm reading on login (using their birth date from the profile), display the energy rating and primary cycles, and show a daily reading card on the home screen. The SDK is @roxyapi/sdk, the methods are roxy.biorhythm.getReading() and roxy.biorhythm.getDailyBiorhythm().

Cursor will scaffold the data fetching, state management, and UI. You review, adjust, ship. Total time from "npm install" to working feature: under 30 minutes.

What you did not have to build:

• Biorhythm sine wave calculations for 10 cycle types
• Phase detection with 8 distinct states (peak, high, rising, critical ascending, critical descending, falling, low, trough)
• Trend analysis (rising, falling, peaking, bottoming)
• Energy rating algorithm (1 to 10 scale)
• Critical day detection and alerts
• Editorial interpretations (hundreds of phase-specific texts)
• Localization into 8 languages
• Compatibility scoring between two people

That is the value of an API over raw formulas.

Why 10 cycles matter for user engagement

Most biorhythm apps only show 3 cycles (physical, emotional, intellectual). The RoxyAPI Biorhythm API includes 7 additional cycles: intuitive, aesthetic, awareness, spiritual, passion, mastery, and wisdom. Four of these are independent secondary cycles (intuitive, aesthetic, awareness, spiritual) with their own fixed periods. The remaining three (passion, mastery, wisdom) are composite cycles derived from averaging pairs of primary cycles, giving users a richer, more nuanced reading.

More cycles means more engagement surfaces. A user checking their physical cycle today might come back tomorrow because their wisdom cycle is approaching a peak. The spotlight feature in the daily endpoint automatically highlights a different cycle each day, keeping the experience fresh without any work on your end.

Frequently Asked Questions

Q: Do I need to understand biorhythm theory to use this API? A: No. The API handles all calculations, phase detection, and interpretation. You send dates, you get structured readings with human-readable text. Zero domain knowledge required.

Q: How does the daily endpoint differ from the reading endpoint? A: The reading endpoint calculates biorhythms based on a specific birth date. The daily endpoint provides a seeded daily reading for consistent "biorhythm of the day" features, with a spotlight cycle and daily message optimized for push notifications and morning check-ins.

Q: What languages does the Biorhythm API support? A: Interpretations are available in 8 languages. Pass the lang query parameter with your request to get localized phase labels, interpretations, and advice text.

Q: Can I use this for a biorhythm compatibility feature? A: Yes. The /compatibility endpoint accepts two birth dates and returns cycle-by-cycle compatibility analysis. Perfect for dating apps, team dynamics tools, or social features.

Q: Is there a free tier to test with? A: Yes. Sign up at roxyapi.com/pricing to get started with the free tier. Every plan includes all API domains, not just biorhythm.

Start building your biorhythm app today

You now have everything you need: a 6-endpoint API covering 10 cycles with editorial interpretations, a TypeScript SDK with full types, and a vibe-coding workflow that lets Cursor do the scaffolding. The entire integration takes one npm install and two API calls.

Get your API key at roxyapi.com/pricing and ship your first biorhythm feature in 30 minutes. Full endpoint documentation is at the API Reference.