Thanks for your comment! ^^
The challenging mode is a mode where you can't regain life. I wanted to make a casual mode with the possibility to go back to the spirit tree without losing the upgrades.
But I had to review my priorities to make a polished and bug free game :).
Edit:
Indeed, for the ghosts, their attacks have very often the priority on you! You have to understand their patterns to avoid being hit. I added a loading animation on each of them (red blue and yellow, + the green mark) to understand when they will attack