It's only a demo, so it's understandable that there is so little, but I have to say after seeing 1.5 million views and a 4 star rating, I was a little disappointed.
So it fell victim to one of the most common mistakes in old flash fighting games, it had the opponent very easily able to be stun locked. While it had a ton of cool features, such as the power up, or flying, man there really not necessary to win whatsoever. Spamming punch in the corner was more than enough to assure victory.
Really this felt more like a tease than a usual demo would, especially since you could see fighters that couldn't be used. Other than that there was only one more problem I noticed, which was the controls were only accessible after entering combat.