Thanks to Martin Gardner's books back in the day we had genious hackers doing just that, recreative programming... until it guided our lifes: GNU/Linux, GNU itself, GNU Emacs, the BSD's, Rogue with the Curses library (and tons of Unix serious stuff), Unix itself to play SpaceWar in a PDP10...

even the ZMachine it's an astounding example of running virtual machines on 8 bit machines 20 years earlier than Java.