Thanks for playing! I'm glad you enjoyed it!
Love the "strike at the heart" achievement idea. I'll test it further and see if it's achievable consistently. "Lightning speed" is a great idea too, but I generally try to avoid time-based achievements or mechanics since one of Serenitrove's core design goals is to stay away from time pressure gameplay (aside from the furnace, which feels fine in that context).
Really appreciate the suggestions though, and I'll definitely look into the core fragment one further :)