there isn't a level designed yet that is so hard that an invulnerability power-up would be required. when the game was faster paced it felt more challenging, and i guess some would say more difficult, to avoid the acid drops and guardians on some levels. but thanks to the tweaked speed of the gameplay and various elements, this is no longer an issue. it all comes down to simple gaming skills. either you have the skills to transverse the levels or you need to develop them. making the game easier would just hurt its integrity. it is a puzzle platformer, it shouldn't be so easy that you can just walk right through some parts.
-another world