I would also go as far as hiding a mini snake game as an easter egg

If you want some code for that I have my own C++ version I made for an ESP32 with OLED screen, it can easily be adapted to most other languages. I did it to get some programming practice. I have Tetris too. All you gotta do is replace the GPIO button inputs with keyboard inputs (or some other boolean on/off user input element) and replace the graphics framework and routines as well (it's only simple stuff like lines, boxes, and setting individual pixels). The whole thing runs in a "neverending" while loop, first checking inputs, then checking collisions, then redrawing any objects that need to move to another position.

I can upload to my GitHub and link them later after work. They do use OOP though, treating each sprite on the board as its own object, and feeding pointers to them into a collision detection routine every game tick. I dunno, some people have a visceral hate for OOP.