# Coinbud

> A paired income and expense tracker installable as a PWA — one shared ledger for two people, with every entry attributed to whoever logged it.

- URL: https://renato-dulog.is-a.dev/works/coinbud
- Author: Renato Dulog
- Category: application
- Tech stack: Next JS, Supabase, Tailwind CSS, ShadCN
- Updated: 2026-06-07

**CoinBud** is a personal-finance Progressive Web App for manually tracking income and expenses, built around a core feature called **Pair Link**.

### What It Is

- A manual income and expense tracker.
- Works great solo, but is designed for **two people sharing one ledger**.
- Every entry is clearly tagged to the person who logged it.

### Why It Exists

Most budgeting tools assume a single user, even though money is often shared. Couples and partners end up with:

- Separate apps
- Separate totals
- Recurring disagreements about whose numbers are correct

CoinBud aims to remove that friction with **one shared ledger**, attributed entries, and no guesswork.

### How It Was Built

**Pair Link by Design**

- Data model and sync layer are built around **“shared by default, solo-friendly”**.
- Two accounts see and edit the **same ledger in real time**.
- Every entry is attributed to the person who created it.

**Calm, Trustworthy UI**

- Visual tone is **calm, restrained, and bank-like**.
- No playful or gamified elements that might undermine trust.

**Feels Like a Native App**

- Mobile-first, installable **PWA**.
- Layout is capped to a phone-like width even on desktop.
- Feels like a dedicated app everywhere, not just a website.

### What Makes It Unique

- **Shared by Design**: Pair Link isn’t a hack or add-on; it’s the foundation of the app.
- **Calm Over Gamified**: No streaks, badges, or mascots, just a clear, steady space for two people to manage money together.
- **Real-Time Sync**: Changes appear instantly for both people, so no one is working with stale numbers.

### Key Takeaway

Building CoinBud showed that good shared tools can’t just be solo tools with a “share” button. They need to be designed around the **relationship** from the start. Thinking of **two users as one unit**, from the data model up, now shapes how collaborative features are approached in every future project.