Castle Agents

I joined Castle as its first hire and helped scale the company. Since joining, we've doubled the team, grew the product to more than 2.5 million users, and raised a Series A. I've worked on all aspects of the product on both mobile and web. This document focuses on my work on agents in Castle.

I led design and contributed to engineering, working closely with another engineer to build AI agents in the Castle Editor.

Agent fan art by @asylbek

Castle is the best way to make games on your phone, but new creators still face a steep learning curve. As AI coding assistants become table stakes for modern software development, we wanted to introduce this capability in Castle. While competitors were betting on costly, fully agentic creation platforms without an existing community, we had a unique advantage; a large, engaged creator network of more than 2.5 million people, who had been creating for years with our tools. We could ship, test, and iterate with real creators from day one.

Oracle - The Prototype

I built a prototype of a chat bot in our discord to understand if there's appetite for AI creation in Castle. At the time our Discord was 25,000 members and growing, so it was the perfect testing ground. After writing a text file explaining Castle and connecting the bot to gpt-3.5-turbo, Oracle was born. People could ask questions about Castle, making games, and writing logic and Oracle would reply in the channel. It was enough signal that this initiative was worth investing in further.

We discontinued Oracle support in Discord to focus on integrating agents directly into the app, and the strong community response was a clear signal that we were moving in the right direction.

Oracle fan art

Operator - The Castle Agent

I worked with an Engineer to build Operator, our agent that can make direct edits to game objects and the scene and edit scripts on desktop. We released Operator to beta, about 30,000 creators got access to it.

I extended Operator to desktop, where it could edit scripts directly, giving more advanced creators the ability to work with code alongside the visual editor on mobile.

The Oracle Discord experiment showed that the Castle community responds well to characters. Building on that insight, I explored many variations of agents.

The feedback was split, some of our most popular creators pushed back on Operator being able to make edits while some creators mentioned how Operator unlocked capabilities in game creation that were otherwise not possible for them.

Above is a 25 page document that's a symbol of the passion our creators have towards building on Castle. One takeaway was that many people see Castle as a way to learn how to program and want an agent experience similar to Oracle that is able to instruct how to make games and not directly make edits.

Guide - The Castle Agent

Using Claude Haiku 4.5, I introduced a new agent to the Editor named "Guide." It's an advisor that answers questions, explains concepts, and can be a brainstorming partner. It never modifies the card, blueprints, or the scene.

Outcomes

Since introducing Agents in the Castle Editor, we’ve driven significant platform growth. Games published has increased 300%, purchases of our in-game currency, Bricks, is up 140% and Bricks spent across key segments has increased by 275%, unlocking a steadily growing stream of recurring revenue and the beginning of a healthy economy.

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About Osebo

Osebo is a Product Designer that writes code. He currently works on Castle, a mobile IDE and social network. Previously, he was a Product Design Lead on Oculus' Horizon Worlds, Nike's .SWOOSH, and a Product Designer at Tumblr. He also built software and hardware for independent radio at Evenings.fm.

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