fixed img path

Author: ruxrux

chapters/OOPs!/chapter.md

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 This tutorial is a quick and practical introduction to Object Oriented Programming in openFrameworks and a how-to guide to build and use your own classes.
 By the end of this chapter you should understand how to create your own objects and have a lot of balls bouncing on your screen!
 
-![balls screenshot](balls_screenshot.png "balls screenshot")
+![balls screenshot](images/balls_screenshot.png "balls screenshot")
 
 ##What is OOP
 Object Oriented Programming is a programming paradigm based on the use of objects and their interactions. A recurring analogy is to see a "Class" as a cookie cutter that can create many cookies, "the Objects". **[MH: I'd take a second to tell people unfamiliar with OOP why they should care.]** Some terms and definitions used within OOP are listed below: