Belly: Virtual Pet on your Apple Watch

A virtual pet for your Apple Watch.

Why

The true origin story is that I got a cat and I wanted to have a virtual version of her to put on my Apple Watch. This then led me to think about virtual pets.

There were plenty of Reddit threads asking for an Apple Watch Tamagotchi, but the existing options were all some combination of ugly graphics, paywalled, or abandoned. I wanted something cute, well-maintained, and most importantly, had my pet in it (yes...).

I chose to build it as a WatchOS-standalone app, as I believed that this app had to live within a small form factor to replicate the Tamagotchi experience. While the app has had reasonable success, I can't comment if this was the right decision - the small form factor heavily limits the scope of features and growth initiatives, and the WatchOS environment is just less powerful than iOS.

What I learned

• AI is powerful. The first live version of the app was written completely via Sonnet 3.5 and Sonnet 3.7, via Cursor. To date I have not written a single line of code unless editing text strings count.
• While heavily relying on AI for implementation, the hard part was still knowing what to fix and why. I don't see this much with Opus 4.5 anymore today, but with the older Sonnet models I found that diagnosis and direction were often times the bottleneck and I had to do manual research to prompt the agent.
• User support emails are pretty fun. It's nice to uncover bugs and help users with their issues, and read the words of love sometimes.
• Distribution matters. I didn't do enough of this (tried US TikTok for a few days but just didn't have the discipline/interest/aptitude to create content) but super thankful for whoever did this distribution for me - the bulk of my users come from China, and I've yet to find out how that happened. They account for 90% of DAU/MAU and 70-80% of monthly revenue. Would never have been such a proud project if not for this large userbase that appeared out of nowhere.
• People pay for things. I don't know why people pay for stuff in my 4D app, but the traction that Belly has is on another level and I can only be thankful for that. Apple's monthly payouts are nice.