Worked on the mamedev/mame repository to enhance emulator fidelity by addressing a critical bug in PHC25 cassette data handling. Focused on low-level programming and hardware emulation using C++, the developer corrected the cassette data polarity and refined input/output timing for the PHC25 system. This technical approach ensured that high and low signal levels were accurately represented during cassette data transfers, directly improving the reliability and accuracy of the emulation. By aligning the fix with an existing issue reference, the work contributed to the maintainability and future-proofing of PHC25 emulation, demonstrating attention to both technical detail and long-term project health.