Change is inevitable. No matter how much you like your software right now, it’s probably going to change tomorrow. And the harder you make it for your software to change, the more difficult it’s going to be to respond to your customer’s changing needs. In this chapter, we’re going to revisit an old friend, try and improve an existing software project, and see how small changes can turn into big problems. In fact, we’re going to uncover a problem so big that it will take a TWO-PART chapter to solve it!