I Built a 3D RPG for My Son’s Birthday — And It Runs Right in the Browser

This wasn’t a side project for the agency. It started as a birthday gift. I wanted to give my son something he couldn’t unwrap from a toy store — so I built him an entire world: a 3D RPG where a spirit cat explores an anime-inspired realm. It’s called CHATTE — Realm of Nekoheim, and the best part? It runs directly in the browser, no downloads, no installs, free, on desktop or phone.

I loved every minute of building it, and technically, it turned out to be a beautiful challenge. Here’s how I did it.

A 3D World You Launch With a Click

CHATTE is built with Three.js (WebGL): real-time 3D rendering in the browser, no plugins, no installs. Open a link and you’re inside — running at 30–40 FPS even on mid-range phones. That’s the part I love most: an open-world RPG with day/night cycles, animated characters, all loading like a web page.

The hero? A tuxedo cat with a scarf and robe. You can wander a Japanese-style village, a cherry blossom forest, a lake, and a castle. And it all changes with time: a full day/night cycle with sun, moon, and fireflies.

From a Clunky Prototype to a World With Soul

It didn’t start this polished. The first cat model? Let’s say it had character — whiskers sticking out in every direction. I iterated, refined the fur, the proportions, the face until it felt huggable.

The world grew layer by layer: terrain and player first, then the castle, the village, the autumn forest, and the lake. I added a minimap, a HUD with health, mana, and stars, and live coordinates so I wouldn’t get lost while building.

Inhabitants and Abilities

An empty world isn’t a world. So the NPCs arrived: villagers moving through town, a wandering mage. And the cat gained powers: dances, a dash for speed, meows, and magic.

Built for Your Pocket

None of this matters if my son couldn’t open it on his phone. So I made it truly responsive: touch controls, vertical-screen HUD, joystick and action buttons within reach. One 3D world, in your pocket.

Why I’m Sharing This (If You’re a Business)

Because at its core, this is what we do at PairProgramming — even if the example is a game: build real, end-to-end digital products that run exactly where they need to. If we can ship a playable 3D RPG in the browser — with real-time performance optimization, 3D rendering, and a mobile version that works — imagine what we can do when the goal is your SaaS, your platform, or your digital product.

CHATTE lives inside ModoJuego, a video game portal, and you can play it for free right now. Want the tech specs? Check out our portfolio page. Got a wild idea for a digital product? Reach out — the best ones come to life with us.

The Part You Can’t See in the Code

There’s a quiet corner of Nekoheim that never makes it into a changelog: a small place in the world made just for the person this was all for. Because the best tech isn’t the one that impresses — it’s the one that says something.

---

By Esteban Aleart, Founder & Lead Engineer at PairProgramming.