Making a full submission only with midi is quite challenging, you did good imo ! The theme are fun, sometimes a little dissonnant but never to the point of getting me out of the track. The sounds are so nostalgic.
I can't really comment on your mix or soundesign, because of the nature of your project I don't think there is much of either, but it never sounded like a big issue ? I think you managed to overcome the limitation of Musescore decently.
Solid, keep the good work !