I like it! ...for the most part. For a free game on the Internet, it's quite impressive!
Given the name, I expected something more akin to a Mario version of a fighter like Mortal Kombat. This was more like a Mario version of Kung Fu or Ninja Gaiden, especially with the wall-to-wall jumping and blind leaps of faith in the latter case!
I thought that a single attack button would have been limiting and tiresome, but that wasn't the case at all and there was a fair variety with the punches.
If there's ever an updated version of this game in the future, then it should incorporate more henchmen enemies than just red shelled Koopas alone.
Moreover, it needs to be a bit more Mario like. Beyond not having any of the classic power ups, it was strange that I couldn't jump onto the Koopas and kick around their shells!
Finally, Bowser is much too difficult. At a certain point, well before his health meter approaches empty: he erupts with a wall of fireballs that literally spans the entire screen and not only kills Mario but knocks around the next Mario that respawns too! Has anyone ever beaten this Bowser?
Beyond those constructive criticisms, I give this game a hearty thumbs up and look forward to any additional future such games!
