for a really simple one?

negotiate your salary. personally I find it hard/nerve racking to do but it's worth it and very very low risk.

it sounds simple but often people are afraid that the offer will be dropped entirely. On average those who negotiate get a few percent more but that compounds fast.

If you're really special or they really really want you then, sure, negotiate hard but even if you're just a normal person in a normal job a polite little note like this in reply to the first salary offer can make a notable difference:

"I am delighted to have been offered the position. I would appreciate if you could consider offering the position at a slightly higher [whatever the term for the local pay scale is], on the basis that this role represents considerably more responsibility than my current role and the qualifications I possess relevant to this position, which I feel are a particularly optimal fit."

They're very very unlikely to discard your application at this point since they already decided they want you. they might say no but very likely they'll offer you slightly more.