Castle Defense Upgrade Hacked unblocked game is free for kids to play online at school for free. Buy weapons, set a tower of the best cannons, and start to destroy the first waves of the slug. Your mission in this Castle Defense Upgrade Hacked is very important. You have to stop them before they escape from the path and enter the castle placed at the end. Don’t worry! You have a great opportunity to use upgrades without paying a penny. Just open the shop, pick anything you want and enjoy the battle. Explore other Tower Defence games if you want.