You could wait until you get the super bomb to gold all the castles. Or you could just gold them all the way up and never replay a single one of them ever.
The bosses are going to zero hp but not dieing. It happened with the turtles arms for me a few times but I destroyed the head and it died. The scorpion I got every single thing to zero and it wouldn't die and the arms wouldn't break. Really great game, Shame this silly bug is preventing me from going any further.
I thought it was a great game. I loved the upgrading system and the difficulty it added, The ability to live-swap turrets from side to side was very actions packed. I look forward to a second game! I'd love to see more towers and more enemies. Perhaps even new maps or ways to play. Very interesting concept indeed, Keep up the good work.
Was a very enjoyable puzzle game. Challenging and fun without being too stupidly difficult. Decent amount of levels and content, I especially loved the incredibly infectious and always certainly fatal disease.