Implementing core gameplay mechanics including player input and movement systems, collision detection and response, physics integration, damage and health systems, scoring and win lose conditions, game state management, and event driven logic. Candidates should explain data structures and algorithms used for entity management, spatial partitioning, collision queries, finite state machines for game objects, and timing models such as fixed timestep and interpolation. For multiplayer contexts discuss authoritative server design, client prediction, latency compensation, rollback or deterministic simulation approaches, and synchronization strategies. The topic also covers code architecture choices such as entity component systems versus object oriented designs, handling edge cases like simultaneous collisions or rapid input, performance optimization, instrumentation and debugging techniques, and approaches to testing gameplay logic and ensuring deterministic behavior where required.
EasyTechnical
65 practiced
You have 1,000 moving entities in a 2D world. Explain how a uniform spatial grid (fixed-size cells) reduces collision checks compared to naive all-pairs checking. Describe insertion, update, and query operations per frame, and how to handle entities that span multiple cells or move between cells frequently.
MediumSystem Design
89 practiced
Clients see ~60ms average latency. Compare strategies for latency compensation in an authoritative server architecture: interpolation, client-side prediction, server-side rewind (for hit detection), and hybrid approaches. For each approach describe complexity, bandwidth/runtime cost, and gameplay types where it is appropriate.
HardTechnical
95 practiced
Explain strategies to ensure deterministic simulation across different hardware, compilers, and platforms. Discuss floating-point nondeterminism, using fixed-point arithmetic, consistent math libraries, controlling compiler optimizations, thread scheduling determinism, and testing techniques to detect platform-specific desyncs.
MediumTechnical
90 practiced
Design an enemy AI FSM with states: patrolling, alerted, chasing, attacking, and fleeing. Include interruptible transitions (e.g., stagger interrupt), variable timers, priority overrides (player stunned), sensing considerations, and strategies to avoid state explosion. Describe data structures and test approaches for correctness.
EasyTechnical
72 practiced
Design a simple health and damage system API for a game object (pseudocode or C#). Include ApplyDamage, Heal, Die, events for UI updates, invulnerability frames, and safeguards to avoid negative health or double-application due to overlapping collisions. Also describe how to propagate death events to other systems.
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