Very cool game! Very polished indeed, in all aspects. And I love that it has a vs mode. Also the overall speed really builds anticipation and puts it back into a gameboy feeling.
Only a minor remark here: the keys are assigned by letter and not by physical key. I've played in an azerty (French) keyboard and it was very frustrating not being able to move backwards until I've realized that the A key was somewhere else. Silly me!