This is Emu 
Emu is based on chip emulators by Andre Weissflog.
The USP of the chip emulators is that they communicate with the outside world through a 'pin bit mask': A 'tick' function takes an uint64_t as input where the bits represent the chip's in/out pins, the tick function inspects the pin bits, computes one tick, and returns a (potentially modified) pin bit mask.
A complete emulated computer then more or less just wires those chip emulators together just like on a breadboard.
This emulator started as a hard fork of C64 emulator example and it shows in places - it is still a work-in-progress.
Fedora:
dnf install libX11-devel libXi-devel libXcursor-devel mesa-libEGL-devel alsa-lib-devel
Ubuntu:
apt install libx11-dev libxi-dev libxcursor-dev libegl1-mesa-dev libasound2-dev
Build using CMake and a modern C/C++ compiler.
Install Emscripten toolchain. Next, run the following commands:
mkdir wasm
cd wasm
emcmake cmake -DCMAKE_BUILD_TYPE=Release ..
cmake --build .
Linux
> build/emu --help
Usage: emu [OPTION...] [ROM.xex]
> build/emu roms/SOTB.xex
Windows
> build/emu.exe file=roms/SOTB.xex