X-FLOW is a mobile game development company established in 2018. We gained recognition after the release of Happy Color, the most popular digital coloring book and one of the most successful ad-driven mobile apps in the world. We take pride in our diverse and talented team and partners, spread across the UK, Cyprus, the Netherlands, and other regions worldwide. We are looking for a Flutter Developer for our flagship project, Happy Color, and for development of new projects. Key Responsibilities: Develop and maintain high-quality Flutter applications with a focus on performance, stability, and clean architecture. Implement adaptive, responsive UI and complex animations with pixel-perfect precision. Design modular and testable architectures. Identify and fix performance bottlenecks (scrolling, rendering, rebuilds). Collaborate closely with designers and backend engineers to deliver smooth UX across iOS and Android. Continuously improve code quality through reviews, refactoring, and automated testing. Requirements: 4+ years of Flutter/Dart experience with solid understanding of widget lifecycle, state management, and animation system. Strong knowledge of Flutter SDK (animations, adaptive UI, rendering, performance tuning). Proficiency in Dart (async programming, isolates, generics, mixins). Experience building custom UI components, pixel-perfect layouts, and smooth 60/120 FPS animations. Deep understanding of Bloc / Cubit / Provider and clean architectural principles (SOLID, Clean Architecture). Hands-on experience with Flutter DevTools for performance profiling and optimization (scroll, rebuilds, memory). Ability to integrate Firebase, analytics, in-app purchases, and push notifications. Understanding of Android/iOS ecosystems and platform channels for native integrations. Experience writing and maintaining unit and integration tests. Russian - C1/higher, English - B1+. What We Offer: Competitive salary and benefits package. Opportunity to work with a talented and passionate team in a creative and dynamic environment. Flexible working hours and remote/office work options. Career growth and professional development opportunities. A fun and inclusive company culture that celebrates diversity and creativity. Join us and let’s create great content together! When you apply for this role, we process your personal data in accordance with our Candidate Privacy Notice (https://xflowgames.com/candidate-privacy-notice).