i don't know what happen but sometime some enemies (mostly small minions like burger, ghost, snowman,others) become almost invincible, this can happen on almost any level regardless of difficulty.
I've just tried several levels of the latest version of the game and everything's working as they should. Which version are you using btw? And can you let me know which levels had the problem? Thanks for playing the game.
i used the browser version. but if you say that the way is intended then nothing i can say. i will add that on the level 7 hard sometime i hit a burger and my armor go to 800+ hit point.
I see, a lot of fixes were made since that version so you may find a few bugs here and there. I guess it's time to update the browser version as well! Stay tuned.