The adjective "achievable" places an upper-bound on difficulty, whereas "challenging" is a lower-bound. I would love a word or phrase that binds difficulty in the sweet spot between these two.
In other words, I am looking for a word or phrase that means "challenging, but achievable."
The context of this question is that I am looking to come up for a replacement mnemonic for SMART criteria, in which the 'A' typically stands for 'achievable.'
I don't like that particular criterion because it doesn't capture the whole story of difficulty-appropriateness. Both bounds are important to me.
None of Frankenstein's goals were [?]; he aspired only to drink his coffee without spilling, and to engender world peace."