Personally, I didn't find the demo fun, and for several reasons.
First thing I noticed, the run animation is god awful.
Second thing, spamming attack and moving left/right is broken.
Third, even holding attack was broken as anything in front of you had zero way to beat you.
Fourth, when holding attack, your hitbox extends behind you, as well. Not enough to prevent getting hit by zombies from behind, but enough to eventually kill them. This also makes it so a swarm of 100 flies can never touch you.
Only good thing really is the pixel h, but I'm just gonna get the gallery for it.