Senior / Principal Game Engineer

Please note that this is a hybrid position based in Cardiff, requiring 3 days onsite each week, with the option for remote work on the remaining days. Part of the Rocket Science Group, Atomic Theory comprises a multinational team of seasoned AAA veterans with roots extending from Blizzard, PUBG, Epic, and Unity. We have a track record of delivering player-centric, AAA-quality experiences, and we're unwavering in our commitment to performance, accessibility, and the meticulous attention to the engineering tools and frameworks that underpin exceptional gameplay. But Atomic Theory is also more than just a studio; for us, it's a sanctuary, a place where our diverse experiences can intersect and combine to carry our solutions to the next level. We're dedicated to aiding studios and publishers in navigating the toughest challenges across today's game development landscape -- and with offices in Albany NY, Brighton UK and Cardiff UK, we thrive at the opportunity to Get Sh!t Done on a global scale. Our passion for gaming is at the core of everything we do, inspiring us to collaborate seamlessly. We're not afraid to take on big challenges and push for bold, innovative solutions. Every decision we make is guided by the goal of delivering maximum value and creating a significant, positive impact on our projects. By consistently going above and beyond, we transform every interaction into an exceptional partnership, building trust and delivering excellence. ABOUT THE ROLE: We are seeking a Principal Game Engineer to join our growing co-dev team. In this role, you will take ownership of the systems players feel most directly: gameplay, UI, 3Cs (character, camera, and controls), and AI. Working across a variety of partner projects, you will design, implement, and refine the systems that drive the moment-to-moment experience, bringing expert engineering judgement to everything from input handling and camera behaviour to UI architecture and core gameplay systems. As a principal engineer, you will set the technical direction in your area, act as a trusted, customer-facing point of contact for our partners, and raise the bar for quality across the wider team. An ideal candidate is passionate about games, has deep experience building player-facing systems in Unreal Engine (or similar), combines expert C++ and C# skills with strong 3D maths, and has a track record of delivering polished, responsive player systems and experiences. WHAT YOU'LL DO: - Player Experience Development: Design, implement, and polish gameplay features, UI systems, and 3Cs (character, camera, and controls) that feel responsive, intuitive, and satisfying in players' hands. - Technical Leadership: Own the technical direction for player experience work across projects, making sound architectural decisions, anticipating risks, and guiding solutions from prototype through to ship quality. - Customer-Facing Collaboration: Act as a senior technical representative to our partners, gathering requirements, presenting solutions, communicating trade-offs clearly, and building the trust that underpins great co-development relationships. - Critical Problem Solving: Apply strong analytical and debugging skills, including profiling and diagnostic tools, to investigate and resolve complex technical issues across gameplay, UI, and engine-level systems. - Mentorship: Support and mentor engineers across the team, sharing expertise in player experience engineering and helping to grow the studio's capabilities in gameplay, UI, and 3Cs. - Code Review: Champion high standards of code quality, performance, and maintainability through code reviews, constructive feedback, and by setting the example in your own work. WHAT WE VALUE: - Expert Software Engineering: Extensive professional experience developing and shipping games, with the depth of judgement expected at a principal level and a history of delivering high-quality, player-facing systems. - Strong C++ and C# Skills: Expert proficiency in C++ a…