I participated in Global Game Jam 2016 with a bunch of friendly people. The theme was "ritual", so we made a game about a time-looped ritual with weird objectives. It works - sort of. We are lacking some mechnics, most notably: characters that die don't get removed which was both a problem and a source of comedy as the room in the game got overcrowded.
The music system fades between the main game theme and the filtered one automatically so that the music "amps up" when you're playing. It also aligns a special effect that tells you how much time you've got to the beat except for the first round where it messes up and hits about 0.3 s off. I also ended up making baby noises for the game in my room - I wonder if my neighbour heard me.