One thing that should be added to the game in my opinion is to be able to see how many levels you have increased since you logged off. I also have a problem that I am not sure if it is the games fault or my internet, but my games seem to be slower even though my graphics are at the lowest (ie. when racing at the stadium, one second in game seems to be around 3-10 seconds in real life)
I have a tip. Go the the latest stage where they're one hit kill, the click on the part where you got to that stage (I dont know what it is called) constantly. IT will give you more gold then letting them drop
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 "Coffee Clicker"){kind=icon}
 "Clicker Heroes"){kind=icon}