My textbook mentions short adjectives like болен which decline by gender - больна, больно, больны. But it also mentions short adverbs like хорошо and сложно which can be used as neuter short adjectives -
adj: Это очень интересно.
adv: Он очень интересно говорил.
Do these decline when used as adjectives? Например,
Мария Николаевна совсем хороша? Я совсем хорош?
I haven't found declension charts for these, so I suspect not. So then, are these words just super-simple-short-adjectives that never decline like болен?