Falling through a hole or miscalculating a jump and hitting the ceiling temporarily stuns him and leaves him vulnerable to a hole scrolling underneath him; if he falls all the way to the bottom of the level, he loses a life.
Falling through a gap or miscalculating a leap and colliding with the ceiling temporarily disorients him and leaves him susceptible to an enemy scrolling underneath him; if he falls all the way to the bottom of the level, he loses a life.