I feel like invincibility frames were kinda busted, I solved a number of puzzles by just placing needles in front of hearts to prevent the player from picking them up, and I feel like I exploited a mechanic as opposed to solving a puzzle. I also feel like I didn't really utilize all of the game's elements. I optimized the fun out of the game. I still think this is a cool idea, but definitely needs to protect the player against themselves.