Engineering

Founding Game Engineer

Generative game systems for a 3D learning world

About us

We're second-time founders and former Google and Synthesia leaders (Search, Voice, and Assistant). We're assembling a core team of engineers, artists, and educators to build the interface between AI and childhood.

The problem we're solving

Kids between 6 and 12 spend hours every day on screens, but most digital content is passive (TV, YouTube) or repetitive (apps, games). Parents want safe, engaging, and educationally positive experiences. Kids crave play, parents crave development and safety, and the industry hasn't bridged that gap.

Our product

Marble is building the first generative learning world. If you've read the Diamond Age, you know what that means. If you haven't, this video will bring you up to speed.

Marble is a 3D exploration game, built in Unity and already in beta. Children explore a procedurally generated world alongside an AI character they talk to through voice. Conversations are open-ended, not scripted. The character isn't a sidekick, it's the core relationship that drives engagement, learning, and emotional investment.

The engineering challenge is unlike traditional game development. The world is generated, not hand-built. The content adapts to each child's interests and developmental needs in real time. And an AI character sits at the centre of the loop, listening and reacting live. Making that feel coherent, responsive, and worth coming back to, at a frame budget, for a six-year-old, is the hardest and most interesting part of the job.

Founders

Guillaume (CPTO): First product hire at Synthesia, where he scaled from $3 to $100M ARR and helped define the category of AI video. Spent 7 years at Google as a PM on Search. Dad of two (ages 7 and 9), giving him a front-row seat to what captivates and educates kids today. LinkedIn.

Lio (CEO): Second-time entrepreneur, founder of Neoplants (raised $25M+ from top-tier US investors). Ex-Google PMM, part of the original Google Assistant EMEA launch team (2017). Creative technologist and product builder with 15 years across tech, storytelling, and consumer launches. LinkedIn.

About you

You think in systems. You'd rather design the rules that generate a thousand interesting places than hand-place one, and you know the particular thrill of watching a procedural system produce something you didn't explicitly author. You understand that the gap between a world that's technically working and one that's alive lives in the systems underneath it, and you love building them.

In corporate speak: we're looking for an exceptional generalist game engineer who's excited to build a new kind of game with AI at its core. You've shipped 3D games. You're a genuinely strong engineer, not someone who just wires up an engine, but someone who understands systems, performance, and real-time constraints deeply. And you build with AI every day: it's in your editor, in your workflow, and you're thrilled to be building a product where AI is the point, not a feature.

What we're looking for, really, is someone who can build the generative systems that make a whole world feel coherent and alive, and wants to use that craft to build something extraordinary for children.

The role

You'll be Marble's first game engineer, owning the gameplay and engine side of a 3D world that's already partway built and in players' hands. That means the systems that generate and drive the world, procedural world generation, content and progression systems, the simulation and rules that make exploration feel coherent and worth coming back to, plus the performance, architecture, and tooling that let a tiny team ship quickly and with confidence.

You'll work alongside our game designer and artist to turn intent into something playable, and alongside our AI engineer, who owns the agent, voice, and LLM backend, to bring the character to life inside the real-time game loop. You own the game; they own the brain; the magic is in how well the two meet.

This is a rare chance to define the engineering foundations of a new category of game, one that goes beyond entertainment to shape the future of learning in the age of AI.

Requirements

You have

• Shipped at least one 3D game (or substantial real-time 3D product) where you owned core gameplay or engine systems end to end.
• Serious engineering depth: strong fundamentals, and real comfort with performance, memory, and systems that run inside a frame budget.
• Strong, professional Unity (C#) experience. Unity is our engine and it's already in players' hands, you've shipped real games or products in it and you'll be productive from week one.
• Live-service experience. You've shipped and operated a game or product that's live with real players. You know what it takes to run one continuously: telemetry, release cadence, A/B testing, crash and performance monitoring, and shipping new content without breaking what's already out there.
• A real, daily AI practice. You're a fluent and enthusiastic user of AI coding tools, and genuinely excited to build a product where AI is the core of the experience.

You're comfortable with

• Building generative and procedural systems, this is the heart of the role. Much of Marble's world is generated, not authored, so you're designing the generators, rules, constraints, and content pipelines that make a vast, adaptive world feel handcrafted, while still sweating the moment-to-moment polish that makes it enjoyable to play.
• Being the first engineer. There's no established architecture, convention, or tooling, you'll set them, make foundational calls with incomplete information, and revise as you learn.
• Integrating a live AI backend. You'll wire our character's voice and behaviour (owned by our AI engineer) into the real-time loop, partnering closely, without owning the agent stack yourself.
• A habit of building tools and pipelines that make everyone else on the team faster.
• Designing for an audience that isn't you. Our players are 6–12. You don't need a child-development background, but you need genuine curiosity about how kids play.

Nice to have

• Deep procedural-generation / PCG chops, noise, wave-function collapse, large-scale world generators, and/or the graphics, shader, and technical-art skills to make a generated world look handcrafted.
• Real-time networking, or streaming audio/voice in-engine.
• B2C product experience (kids-focused even better).
• A side project, indie game, or game-jam history that shows you build for love, not just for work, especially if it uses AI as part of the game itself.

Genuinely optional

• Your hottest take on a procedurally generated game that actually nailed it. Minecraft? Spelunky? Hades? No Man's Sky? Tell us why, we'll judge you either way.

Work conditions

• Salary £90–130k depending on experience.
• Strong equity component (this is a founding hire).
• In-person work from London Kings Cross, open to remote for the right candidate.
• The chance to shape your own engineering environment from day one.