Called "Jump Rope Game" for short.
This was the first game I finished outside of a game jam. It was made to prove exactly that. I asked myself "what is the simplest possible game you could make and still call it a game. I came up with the concept for a one-button jump rope game, reused some assets from another unfinished project, and got to work. I remember it was 9:00 on a school night, close to when I should be going to bed. I told myself "that's fine, this will only take about 20 minutes" and I held myself to that.
I recommend this exercise! I think it's a fun thought experiment to define how small a game can be while still being a game. Can you go smaller than this? I don't know, but if you find a game smaller than Jump Rope Game I'd love to see it!
If you wanna see "part 2" of this jump rope saga, check out JUMP.