One of the nicest collection of handheld emulators I have seen, and runs in a browser so enables play on a range of devices. I was even able to play on my Xbox One X using Edge browser (a few issues on Xbox with some of the games though including crashing webgl on certain games when attempting full screen mode, Octopus crashed but Donkey Kong dual screen worked in full screen for instance).

I just spent the last hour playing Donkey Kong dual screen and Octopus with my young son and reliving my youth. Seems I still have the muscle memory for those games even 40 years later.