ConsulCaesar: I finished Kingdom Rush when it was first published on Flash game websites (but not with the max score -some levels were insane). It's a really fun tower defense.
Do you know if this version adds new stuff, compared to the free game from back then?
Yes, it's surprisingly excellent :)
I played the flash and mobile versions for a while and those have premium content you pay for. I can't remember exactly what that entailed with the kongregate flash version, but I think it's similar to the mobile version: you have to pay to get the extra heroes and levels.
In the PC version, all the heroes as well as all the bonus levels / mini campaigns (about 10 levels total with 5/6 unique bosses) are unlocked from the start. Well, unlocked in that you don't have to pay for them. You still need to unlock them ingame by reaching certain stages of progress. E.g. the final 3 heroes are only unlocked once you finish the main campaign.
It's pretty cheap too. I bought the whole game for less than what it costs to unlock 3 of the 9 heroes on mobile!
Perhaps more importantly, the PC version is simply superior from a technical perspective. It runs/controls far, far better and with crisp full hd support. To me at least the 'free' flash version compares very poorly to it.
OT:
finally killed one of the final bosses (from bonus mini campaign after finishing the main game)
but the other demons, which I ignored to deal with the boss, have a cloning ability and subsequently
completely overwhelmed me got it on a another attempt though, but I was concentrating too hard to take a screenshot :P
edit: notice hellboy armwrestling in the top right, and the evil sorcerer suspended in a cage - he is/was the final boss of the main campaign XD The game is full of little details and references like this.