You did a great job making the spirit mode something the player wants, it has so many advantages over the human mode. I liked that the human takes longer to attack, it creates an initial tension when an enemy comes, but once you get enough energy it's a burst of excitement and relief! Also good tutorialization, you didn't rely only on the text at the top, you also used the level to teach mechanics - the 3 levers was a clever way of showing the benefits of spirit mode.