A strange little side quest
If Cannon Balls 3D sends you down a curiosity rabbit hole, start here. Doom changed game design and distribution in 1993 by separating its engine from content and spreading widely through shareware. Another piece of context lands nicely beside it: Spacewar! appeared on MIT's PDP-1 in 1962 and became one of the earliest influential computer games shared among programmers. Not bad for a few facts hiding behind a Play button.