City Forge: Mobile City Builder
Simulation · Unity · iOS & Android · Live Service
City Forge is a mobile city-building simulation with supply chain management and resource allocation. Nine Pixels engaged from pre-production through launch and continues live ops 18 months later. Started with a 6-week prototype phase focused entirely on solving the retention problem that killed the client's previous title.
The client's previous city builder was discontinued after launch, the common simulation genre problem of losing players after initial construction. Design challenge: meaningful mid- and late-game loops retaining past day 30. Technical challenge: hundreds of simultaneous building simulations with smooth mobile performance.
Retention design combines a citizen satisfaction system (constant small optimisation challenges), async social mechanics (visiting other players' cities), and time-gated events. City simulation runs on a custom hand-rolled ECS-style component system. Isometric low-poly art designed from the start for mobile performance with strict polygon budgets and GPU instancing.
Day-30 retention of 22% in a city builder is almost unheard of. Nine Pixels solved the design problem that killed our last game.