I Built a 3D RPG for My Son’s Birthday, And It Runs Right in the Browser
Instead of buying a gift from a toy store, I coded an entire world for my son: CHATTE, Realm of Nekoheim, a 3D anime-style cat spirit RPG that runs free in the browser using Three.js. Here’s how I brought it to life, layer by layer.
July 13, 2026
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.
FAQ
What’s CHATTE built with?
Three.js (WebGL): real-time 3D rendering directly in the browser, no plugins, no installs. That’s why it opens with a link and works the same on desktop and mobile.
Is it free to play?
Yes. CHATTE is free and runs in the browser with no downloads. It’s hosted on ModoJuego, a video game portal.
Does it work on mobile?
Absolutely. It’s truly responsive: touch controls, on-screen joystick, action buttons, and a HUD optimized for vertical screens. Same 3D world, in your pocket.
A 3D browser game can’t run smoothly, right?
Not if it’s built right. CHATTE runs at 30–40 FPS even on mid-range phones, with an open world, day/night cycles, and NPCs. Real performance optimization is the hard part, and that’s what makes the difference.
Do you build this kind of software for companies?
Yes. Even though this example is a game, it’s exactly what we do at PairProgramming: custom digital products, end to end, built to run where they matter most. Got an idea? Let’s talk.
Related articles
Table 7 requested another item: the cost to a bar of paper-based management.
Table 7 ordered a schnitzel without cheese because there is a celiac customer. On the way from the dining area to the kitchen, the "no cheese" request was lost. This bottleneck, how information travels between the dining area, kitchen, and cash register, is where a bar's profitability slips away. What we built to solve it.
Desarrollo de SoftwareCustom CRM vs. SaaS (Salesforce, HubSpot, Pipedrive): How to Choose the Right Fit
The "Salesforce or custom-built" debate rarely ends well. Either you end up with an expensive CRM nobody uses, or you build something bespoke that quickly becomes unsustainable. Let’s cut through the noise and make the right call.
Desarrollo de SoftwareReusable platforms: the engine behind 5 different verticals (and how to design them right)
When building your second or third product in a family (event CRM, real estate CRM, auto shop CRM), you realize 70% of the code is the same. There’s a right way, and a wrong way, to reuse it. Here’s the right way.