Built an NES emulator from scratch, implementing all 151 official 6502 opcodes plus the PPU and APU subsystems to run commercial ROMs (Super Mario Bros., The Legend of Zelda, Metroid) at a stable 60 FPS. Engineered a real-time rendering pipeline in OpenGL/GLFW that translates PPU framebuffer output to modern GPUs within the NES's 16.6ms frame budget.