Worked on stabilizing complex card exile interactions in the magefree/mage repository, focusing on improving the reliability of card casting and state management in a Java-based card game engine. Addressed a critical bug by refining how exiled cards are handled during castMultipleWithAttributeForFree, ensuring only valid cards remain eligible for casting and aligning the logic with established engine patterns. In the kadai-io/kadai repository, enhanced data integrity by repairing copy constructors and restoring assignment order in model objects, which improved deterministic behavior and reduced hidden state drift. Applied object-oriented programming and software design principles to deliver robust, maintainable solutions across both projects.