> if all it did was substitute for X, and behave exactly the same way? LSP is about behaviour existing in the supertype. Adding behaviour doesn't violate LSP

> if all it did was substitute for X, and behave exactly the same way? LSP is about behaviour existing in the supertype. Adding behaviour doesn't violate LSP. > In a graphics program, an ellipse and rectangle are substitutable in that they have a draw() method and others, so that they plug into the framework. The behaviour in question means it draws something. It can draw something different every time, and not violate LSP here.