My game, Pit of a Thousand Bowling Balls now has achievements and a leaderboard!
It was a bit of a hassle learning the API and some basics for Godot that I was completely ignorant of, but the system is remarkably simple and robust once I got past those issues! I'm super excited to throw some achievements into my next game (it's really coming together, and it's gonna be a lot bigger and better than the first one!)