This is a NES emulator which displays just a background like below.

Free and legal ROMs are from http:https://hp.vector.co.jp/authors/VA042397/nes/sample.html.

Install SML# (see https://www.pllab.riec.tohoku.ac.jp/smlsharp/?Download https://smlsharp.github.io/ja/downloads/), then

$ brew install sdl2
$ make
$ ./main emu.nes
$ ./main sample1.nes

The execution speed is very slow 😅