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.
Err... My original intent wasn't to compare the concept of a "Knock the tower down" game in and of itself to Angry Birds, but merely Crush the Castle, as it was the first famous game to market the concept.
Crush the Castle all the way ! Angry birds stoled the idea, and he have a success because he is on smartphone, the flash games have invented all the smartphone games !