This is a NES emulator which displays just a background like below.
Free and legal ROMs are from http://hp.vector.co.jp/authors/VA042397/nes/sample.html.
Install SML# (see https://smlsharp.github.io/ja/downloads/), then
$ brew install sdl2
$ make
$ ./main emu.nes
$ ./main sample1.nes
