I Built an App to Encourage My Kids to Invest — Just One HTML File

One thing that school doesn’t teach you (not even high school) is how to manage your personal finances.

As my eldest son’s birthday was approaching, we suggested that instead of asking for physical gifts, he ask for their equivalent in money. That way, he gathered a decent amount of capital for his first investment adventure.

I explained to my kids that investing is like having a magic box that generates more money over time. To make it more visual and interactive, I decided to create a small app where they could see their investment grow day by day.

From Idea to App

My first idea was to build a physical piggy bank with a display, showing the accumulated amount. However, that mixed up the concept of saving with investing, and also required buying extra hardware.

So I looked for a quicker, cheaper way: revive an old smartphone and create a simple app using plain HTML.

The result was D-investments, a mix between Diversions and Investments.

How It Works

The app is essentially a single HTML file that installs on the phone as a PWA (Progressive Web App).

The phone is attached to the fridge and works as a panel or dashboard where my kids can see their money growing each day.

I act as their investment agent, assigning realistic interest rates — high enough to keep them motivated, but moderate enough to reflect how the real world works.

Configuration Screen

The app includes a screen where you can enter:

• The kids’ names

• The invested amount

• The interest rate

• The start date

Configuration screen

With that data, the app automatically calculates and displays:

• Daily gain

• Weekly gain

• Monthly gain

• Total updated balance

Dashboard view installed on the fridge showing daily growth.

Materials Used

• An old smartphone

• A suction mount to attach it to the fridge

• The D-iNvestments app, in HTML format

Installation

The process is as simple as opening the link from a smartphone and tapping “Install” when prompted by the browser.
From then on, it behaves like a native app.

Access the app:
Click here to open and install D-investments

Final Reflection

The goal wasn’t just to teach my kids the value of money, but to show them visually how investment and time work as allies.

Each day, as they watch their small fund grow, they grasp the magic of compound interest — and that, more than any gift, is a lesson I hope will stay with them for life.