IMO, the levels that are the hardest are the ones with only just presents and extra click bonuses. A tip from me: just stay patient. wait until you can hit a big group to click. 5/5 and wants a sequel!
I want to like this game, because the idea is good, and its just fun to start out in it... but too many things are wrong, like difficulty spikes, lag, Annoyingness of the near-unwinnable fight near the beginning...you know the one...,grindyness, and the 2 weapons stupid targeting scheme (how hard is it to aim two guns at the same target?!), for this to be good. 3/5 for a decently fun game, but it just gets repetitave toward the end.