Nguyen Trong Toan developed the core gameplay engine for the d23-java/seabattle repository, focusing on a Battleship game with both two-player and bot modes. Using Java and object-oriented programming principles, Toan implemented configurable board sizes, optimized ship placement, and a turn-based shooting system. The project included enhancements to the command-line interface, such as colored output and screen clearing, to improve user experience. Toan refactored critical game logic for maintainability and scalability, laying groundwork for future features. The work delivered a robust, interactive foundation for game development, demonstrating depth in game logic design and user interface improvements within a one-month period.