First of all, this is a * spoiler * for our entry. So if you haven't played Earworm Jam yet, please do so first!
https://ldjam.com/events/ludum-dare/50/earworm-jam
https://ldjam.com/events/ludum-dare/50/earworm-jam
With the shameless ad out of the way, we can get to the topic at hand, making your mechanics obvious. For our game, we decided to make one of the main mechanics not so obvious and even somewhat counter intuitive to what the UI is telling you. There are hints as you get combos that getting high combos is a positive thing for the worm that is chasing you. But in being cheeky, I decided to make it RNG on what messages you get and add in a requirement to play some first before they will start having a chance of showing up. There are some really obvious ones that flat out give away that the worm is the one complimenting you on your combo streaks. However, for games jams it's definitely not in the players favor to require multiple playthroughs to discover the mechanic.
That being said, I'm torn on if it was a good idea or not to make our game an anti-rhythm game without explicitly telling the players. The thought of a player discovering the mechanic while playing and having that AHA moment satisfies me greatly. In the end, I think it would have lead to a better player experience if we would have just told the player the mechanic since it's not intuitive and many players never figured it out. At the very least, the hints should have come sooner and been a lot more obvious.