If you're running low on health then follow these simple steps to refill health!
1. Save the game to one the data slots.
2. Exit the game.
3. Load the game and have full energy.
Pick up twenty crowns on each level and a box marked with a question mark will pop up on the level selection screen. This option will let take on any of the bosses without needing to play through the level each time. The markings on the door let you know which boss you are about to fight.