I. too, took a bit to figure it out, without any on-screen prompts.  There also was no score or progression metaphor, but I thought it was an interesting mechanic and was solid for what it offered. I found no audio with it, and it was thin on the theme, unless the skulls were "you." Credit for being a single contributor.

I think I figured out how to play it. You use the mallet to hammer a crack in the floor and then hit again to explode at the right moment to kill skulls touching the heart.

It would be nice to have text to instruct you on how the game is played.

Interesting idea but this is sort of like "Missile Command". I can't seem to see where this fits with the Game Jam Theme.