I did pong in rust to learn some rust, and it got me thinking how, doing pong was really easy (as an experience programmer) but if you wanted to do pong "properly", say supporting 4 different platforms, 5 languages, proper settings menu and high score table, supporting all manner of screen resolutions, full screen and windowed, sound, all popular controllers (keyboard, mouse, mobile input, game pads, joysticks) etc etc etc
I've often said that a team couldn't ship a production-ready version of Tic-Tac-Toe in less than a month...even if the implementation were already written.
then even pong is pretty hard.