Not bad.
Just out of curiosity, how "retro" are we talking here? 'Cuz this style doesn't remind me of that of any famous anime artist from the past...
It DOES, however, remind me of OEL artist Katy Coope, whose art I don't particularly care for, but that's just my opinion.
9/10 for nostalgia.
P.S. It's Sonic's birthday!!!