Nice ideas. Many people in jams don't even listen to the sounds, but their own music that's playing in the background, especially if they are a streamer, so I don't take audio as very high priority and should be done last in any project, if there's even time to make sounds. I thought of some difficulty-increasing elements like puddles or obstacles you pull the cart through, but I was really on my last minutes before going to sleep and I just joined the jam at the very end when I could, so I just left it at where it was at that point.