A buddy of mine and I had a small debate on the soon mentioned situation and I'm curious if I may have screwed him over on a misunderstanding of how the stack works. Consider the following situation:
I attack with a X/X creature that my opponent can't block. After attackers/blockers have been declared, my opponent casts Silverstrike and then I respond something like Titanic Growth (as an example), and it contains the key phrase "...until end of turn"
Is this a legal response? My line of thought is that my instant will resolve at "end of turn" which will allow his to resolve then killing my creature. Or is it that what I did made no difference and it resolves right away allowing his instant to resolve still killing mine before I can attack?