challenging
v.v. difficult in a way that tests your abilities or keeps you interested. You use this to describe a task that is hard but often rewarding.
v. demanding a high level of physical or mental effort; testing one's abilities or endurance. Often carries a positive connotation of growth or stimulation rather than mere difficulty.
The new project is very challenging but I enjoy it.
Finding a solution to the budget deficit proved to be a challenging task for the new committee.
While the technical requirements of the role are undeniably challenging, the position offers an unparalleled opportunity for professional development within a competitive industry.
From Middle English chalengynge; equivalent to challenge + -ing.
Typically used as an attributive adjective before a noun or a predicative adjective after a linking verb.