A Nintendo Entertainment System emulator written in Go with a platform-neutral core covering the MOS 6502 CPU, PPU graphics, five-channel APU audio, cartridge memory, and controllers. It supports six mapper families—NROM, MMC1, UxROM, CNROM, AxROM, and Color Dreams—and runs in the browser at 60 Hz through WebAssembly and Ebitengine.
The browser build keeps locally selected ROMs on the user’s device, supports keyboard and touch controls, streams 44.1 kHz audio, and offers an optional CRT display treatment. Its release build generates a launcher for bundled ROMs, ships only an explicit asset allowlist, strips debug data and local paths, and enforces a compressed WebAssembly size budget.
The hard part is coordination rather than instruction decoding: CPU, PPU, and APU timing must remain aligned while mapper hardware changes which program and graphics banks are visible. Small timing errors surface as broken raster effects, unstable audio, or game-specific compatibility failures.