Let's be honest, it seems a bit silly, but getting 3 stars on the last level is a proper challenge. I beat the boss right as he was just a millisecond from striking me, it was great. I was level 81 by then!
Winning trap setup:
From left to right, 4 fireball traps, 2 tesla traps in the middle, four slow down traps, two tesla traps, four slow down, repeat those with as much money as you have. You can go eat a sandwich.
Woop woop! The bugs were annoying me. But then, as I was struggling to beat the final boss...when he was at about 1/2 health, it just declared me the victor and said I won the game! Yay to bugs!
5/5 game, lowered to 4/5 because of bugs - for instance, the 'incorpereal enemy' that shows up some levels who has infinite hit points and can't damage, and prevents level completion; the complete stupidity of AI and general weakness of allies, ...
Like a boss? I fully upgraded and chopped the beanstalk with 11,000 clicks and only a few hours of waiting..how the hell is anyone supposed to click this 50,000 time?!?