Archive.org has launched a section where you can play thousands of old MS-DOS games within your browser. So much for productivity. I should mention though that some of these games have emulation issues because they weren't developed for modern processor architecture so sometimes they'll run too fast. I ran into that a few times. Also, not all games have instructions, although sometimes people will post helpful information below in the comments.
https://archive.org/details/softwarelibrary_msdos_games&tab=about
https://archive.org/details/softwarelibrary_msdos_games&tab=about