So... has Rovio Mobile paid royalties to joeybetz or something or was the game public domain? While the physical game concept can't be copyrighted (defense games, Fighting games, FPS, RTS, etc), Angry Birds shamelessly copied every single game design and mechanic from Crush the Castle. Swap projectiles for birds, a catapult for a slingshot, and pigs for nobility. It makes me slightly indignant as a loyal and long time fan of CtC.