it is posible that the game runs choppy even tough it plays fine on my end. I had some problems uploading the game as WebGL due to size and browser memory overloads. I provided a downloadable version if you want to try. It is more stable.
As far as I know there is a particle effect for when you hit a zombie, but maybe it is not working well in Web on some devices.
As you indicated, I should have mentioned that if you kill 20 or 25 zombies I believe, you can unlock an ending. My bad.
Thanks a lot for playing my game and leaving such good feedback (. ❛ ᴗ ❛.)