Play abandonware games
Technically, abandonware games are games not supported anymore from their developers. If the original developer company is no more and if the game is so old that no one cares for it anymore, it becomes "abandoned". Usually, no one bothers about abandoned games but the retro gaming community, that's why it's so easy to find online games developed for now defuct platforms like Commodore 64, MS DOS, Sega Genesis, Windows 3.1, Spectrum, Amstrad CPC, etc. There were so many different home computers and consoles in the 80s and the 90s that abandonware became a niche phenomenon. If you're into abandonware for DOS and Windows, take a look at Abandonware DOS.
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Mario Bros VGA
platformer / arcade
Dave Sharpless

The Lost Vikings
platformer / action puzzle
Interplay Productions

Dark Horizons Lore: Invasion
simulation / first-person shooter
GarageGames

Strip Poker Deluxe
card game / strip poker
Eagle Rock Enterprises

Railroad Tycoon
simulation / management
MicroProse Software

Super ZZT
action / action puzzle
Epic MegaGames

ZZT
action / action puzzle
Epic MegaGames

Dreamweb
adventure / point & click
Creative Reality

Strip Poker 2
card game / strip poker
Artworx Software

King of Chicago
adventure / action-adventure
Cinemaware

PC*Bert
action / arcade
JROK

Strip Poker: a Sizzling Game of Chance
card game / strip poker
Artworx Software

TV Sports: Baseball
simulation
Cinemaware

Captain Comic 2: Fractured Reality
platformer / metroidvania
Michael A. Denio

It Came from the Desert
adventure / action-adventure
Cinemaware

Mario and Luigi
platformer / arcade
Mike Wiering

Playhouse Strip Poker
card game / strip poker
Eurosoft

Genocide
strategy / artillery
PyroSoft

S.D.I.
action
Cinemaware

The Three Stooges
action
Cinemaware

TV Sports: Boxing
action
Cinemaware
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