When adding cones and the other requirements in our world would have to change our program quite a bit. Starting with rules for our cones. They cannot have blocks stacked on top of them; they might be able to have cones stacked on top of each other; cones have the ability to be put on top of blocks. If we still have small and big blocks we would have to determine the size of the cone in order to make sure that we can stack on small blocks.

We would need some type of statement to check what is to the right and left of each object and be  able to keep track of the objects locations. 
The sentence structure would have to change because our new left and right words. 
Implementation of new validate and acting rules to cover our new cones and what we are allowed to do with them.
New resolve references would need to be created to cover our new cones and their colors. If we were to have different size cones we would also have to add those to our sentence structures.