I, Ball II

After rescuing their people and surviving (in the first game), the Ball race
wish to discover something about their history and heritage. You have been
sent down mines, to explore 50 screens, on each of which you must collect a
key and reach the exit. You also have to pick up a sacred artifact on every
5th level.

Your character is very bouncy, requiring small movements in order to keep
control. You can shoot at the surrounding enemies and collect weapons,
although the initial one only shoots horizontally. There are many pickups on
offer, including extra lives, bounciness boosts and opposition-slowers.