Some may be grinding the game for all the achievments, here's a little guide on how to get the "Hearty" achievement.
1. Enter the game
2. Equip the "Twin Heart" Charm in the equip menu
3. Exit out the Equip menu
4. Start spinning around in circles until Genie appears.
5. Go to a level and play it on simple
6. Yay nine hearts hope this helps :)