Castle such as these were build with the outward walls at an angle to dissipate the inertia of incoming cannonballs. Instead of the cannonballs hitting the walls directly and causing as much damage as possible, the cannonballs would ricochet off of the wall and over the castle, causing considerably less damage. The walls are at an angle to cause even greater difficulty in sieging the castles, as they would allow more archers along the walls of the castle to defend and reduce the area in which the opposition would be taking below, making it more likely for the archers to hit someone or something. If anyone is interested, I'll gladly add details to the molds for you.