How I built a full-scale fortune-telling app during my company break using only my smartphone, without looking at a single line of source code, just by speaking in Japanese
[True Story] How I built a full-scale fortune-telling app during my company break using only my smartphone, without looking at a single line of source code, just by speaking in Japanese
by geminipro-sensei
Introduction: Who should read this
You have no knowledge of programming
But you want to try building an app
You only have a smartphone (or cannot use a PC freely)
You don't want to spend any money
This article is written for people like you.
This is all I actually did.
I just kept talking to Claude (AI) on my smartphone in Japanese. I didn't read a single line of source code. I did it secretly during my company break. The cost was zero yen.
As a result, the full-scale fortune-telling app "Fate Layer" was completed.
👉 Click here for the Web app version (free)
👉 Android APK download (free)
App Overview
Fate Layer is a fortune-telling Web app & Android app where AI integrates Four Pillars of Destiny, Nine Star Ki, Numerology, Horoscope, and Name Analysis to generate full-scale readings.
Here are the main features.
5 types of divination (Today, This Week, This Month, This Year, Comprehensive Reading)
Name Analysis (Automatic calculation of Heaven, Earth, Human, Outer, and Total strokes)
5-language support (Japanese, English, Chinese, Korean, French)
Uses completely free Groq API (no credit card required)
PWA support (can be installed and used on smartphones)
Android native app version available (download and install the APK)
Night sky background animation (Canvas drawing)
All I used was my smartphone and Claude. I didn't write a single line of code.
Table of Contents
1. Motivation and Development Environment
2. Development Process (Interaction with Claude)
3. Points Where I Got Stuck and Solutions
4. App Specification Details
5. How to Obtain a Groq API Key
6. How to Publish as a Web App
7. How to Install as an Android App (APK)
Summary: The complete version of the production process is on Brain
1. Motivation and Development Environment
In the note 'Geminipro-sensei', I verify and introduce what can actually be done using AI tools.
The rules for this challenge were as follows:
Smartphone only (no PC use in principle)
Instruct Claude only in Japanese
Do not read or write any source code
Work on it secretly during company breaks
Zero cost
I tested how far I could go in building an app under these rules.
These are the only things you need.
Smartphone (Android or iPhone is fine)
Claude account (free plan is fine)
GitHub account (free)
Cloudflare Pages account (free)
Groq API key (free, no credit card required)
No programming knowledge is required at all. You can do everything with just a smartphone.
2. Development process (interaction with Claude)
Step 1: Create the app framework
By simply telling Claude to 'make a fortune-telling web app' at the start, a complete set of HTML files was generated. I was surprised that it came with a night sky animation background, a form, and a result display area right from the start.
Step 2: Implementing fortune-telling logic
When I asked it to 'add a name divination feature,' it automatically generated calculation logic that included a stroke count table for kanji. It automatically calculates the five elements—Heaven, Earth, Human, Outer, and Total—and reflects them in the fortune-telling results.
Step 3: Multilingual support
When I told it to 'support 5 languages,' an I18N object was added, and all text became compatible with language switching.
Step 4: PWA support
With just one sentence, 'make it installable on smartphones,' a manifest.json and a Service Worker were added. After several exchanges regarding the icon design, we settled on a rotating star-shaped sigil design.
Step 5: Struggling with the API key issue
This was the biggest hurdle. I tried various APIs like Gemini and OpenAI, but I gave up on them one after another due to free tier limitations or complex settings for Japanese accounts. Eventually, I found that Groq is completely free, requires no credit card, and runs fast and stably.
Step 6: Converting to an Android native app
I used a tool called Capacitor on my PC to convert the web app directly into an Android APK file. This allowed me to install it on my smartphone as a native app.
3. Points where I got stuck and solutions
Problem 1: Various APIs could not be used
Cause: The free tier for the Gemini API is restricted in Japan in some cases. OpenAI is paid.
Solution: Switched to Groq. You can use high-performance models like Llama and Gemma completely for free.
Problem 2: PWA cache would not update
Cause: The Service Worker was caching the HTML and kept returning old code.
Solution: Changed sw.js to network-first (cache: 'no-store').
Problem 3: Provider buttons overflowed the screen
Cause: Buttons were added while flex-wrap was set to 'nowrap'.
Solution: Changed to 'flex-wrap: wrap' to make them wrap into two lines.
4. App specification details
Types of divination
Type Content Comprehensive Reading Integrates Four Pillars of Destiny, Nine Star Ki, Numerology, Astrology, and Name Judgment Today's Fortune Daily flow of love, work, health, and money This Week's Fortune Flow of the first and second half of the week, chance days, and caution days This Month's Fortune Overall flow of the month and important turning points This Year's Fortune Overall flow and guidelines throughout the year
Name judgment calculation formula
Category Calculation Method Heavenly Luck Total strokes of the surname Earthly Luck Total strokes of the given name Human Luck Strokes of the last character of the surname + first character of the given name Outer Luck Heavenly Luck + Earthly Luck - Human Luck Total Luck Total strokes of the full name
AI models used
Provider Model Fee Groq llama-3.3-70b and 4 other models with automatic switching Completely free
5. How to obtain a Groq API key
console.groq.com Open in your browser
"Sign Up" -> Register with your Google account
Top-right menu "API Keys" -> "Create API Key"
Copy the displayed key (starting with gsk_) immediately
*The key is only displayed in full immediately after creation. Please make sure to copy it right then and there. No credit card required, completely free.
6. How to publish as a Web App
Preparing the GitHub repository
Create an account at github.com
"New repository" -> Enter a repository name
Upload index.html, manifest.json, sw.js, icon-192.png, and icon-512.png
Click "Commit changes"
Cloudflare Pages settings
Open dash.cloudflare.com
"Workers & Pages" -> "Create application" -> "Pages" -> "Connect to Git"
Link with GitHub and select the repository
Click "Save and Deploy"
From then on, it will be automatically deployed just by uploading files to GitHub.
How to install as a PWA (Android)
Open the deployed URL in Chrome
Top-right "⋮" -> "Install app"
An icon will be added to your home screen
7. How to install as an Android app (APK)
You can download app-debug.apk from the link below and install it on your smartphone.
Installation Steps
Download the APK from the link above
Tap the APK in your file manager
If prompted to allow 'apps from unknown sources', select 'Allow'
Tap 'Install'
*Since this is not via the Google Play Store, a warning will appear during installation, but there is no problem.
8. Summary
Just by talking with Claude, I was able to achieve all of the following:
Full-scale fortune-telling logic (5 types of divination + name analysis)
5-language support
Completely free Groq API support
Night sky animated background
PWA support (can be installed on smartphones)
Free publication on Cloudflare Pages
Android native app (APK) conversion
We are in an era where you can do this much just by talking to Claude, even without programming knowledge.
The complete version of the production process and source code are on sale at Brain!
In this article, I introduced the overview and usage of the app, but for those who want to build a similar app themselves, I am selling content on Brain that summarizes the entire interaction with Claude, the source code, and the complete procedure for creating an APK.
Includes all actual interactions with Claude
Completed source code (index.html, manifest.json, sw.js)
Complete procedure for converting to an Android app APK
Details on points where I got stuck and their solutions
💰 Price
980 yen (early bird price limited to the first 5 days after release) → 1,980 yen (regular price after 5 days)
Buy now and save 1,000 yen!