I don't want to be a downer, but i didn't like it very much.
I know this is probably a work in progress so i will try to be a little gentle.
This is my opinion so far.
-Goomba should point forward or have a greater rate of fire, since having to move and shoot at the same time to aim forward is kind of annoying.
-From a conceptual point of view... koopa troopas shouldn't be allied with Mario. Toad, on the other hand, as the regular enemy cannon fodder would have been more fitting.
-Technically, it works as a game but it's kind of bland. Maybe if you added some power ups or something of that kind.
Anyways, it was still kind of entretaining so i think you could get a better result with the gelp of the critics on this site.
Best wishes and happy holidays.