Senior Principal Game Engineer (Hybrid, Cardiff)

About the role

Atomic Theory is looking for a Principal Game Engineer to join its co‑development team in Cardiff. You will own the core player‑facing systems – gameplay, UI, character, camera, controls and AI – across multiple partner projects. The role combines deep technical expertise with direct customer interaction to deliver polished, responsive experiences.

Key responsibilities

• Design, implement and polish gameplay features, UI systems and the 3Cs (character, camera, controls) to create intuitive player experiences.
• Set technical direction for player‑experience work, make architectural decisions and guide solutions from prototype to ship quality.
• Act as the senior technical liaison for partners, gathering requirements, presenting solutions and communicating trade‑offs.
• Diagnose and resolve complex technical issues using profiling, debugging and engine‑level tools.
• Mentor and review code for engineers across the team, championing high standards of performance and maintainability.

Required profile

• Extensive experience shipping AAA‑quality games with a focus on player‑facing systems.
• Strong C++ and C# expertise, writing clean, efficient code.
• Deep understanding of 3D mathematics, linear algebra and geometry for cameras, movement and animation.
• Proven ability to communicate technical concepts clearly to partners and stakeholders.
• Passion for gaming and a keen instinct for what makes controls, UI and gameplay feel great.

Required skills

• C++ and C# programming.
• Unreal Engine (Gameplay Framework, UMG/Slate, input and camera systems).
• 3D mathematics and physics.
• Unity engine experience (optional).
• Console development experience (PlayStation 5, Xbox Series X/S, Switch).

What we offer

• Competitive salary and comprehensive benefits, including private pension and optional medical coverage.
• Hybrid working arrangement – three days onsite in Cardiff city centre, two days remote.
• Annual research credit for personal development and professional training.
• Generous family leave (6 weeks maternity/paternity/adoption) and a no‑crunch culture.
• Weekly team lunches, fully equipped lounge with consoles, and a supportive, creative environment.