In this chapter, we learned how to wire up an LED and how to use the REPL to modify our robot's state in real time. We understood what software is involved when working with complex hardware. We also looked at what makes Johnny-Five stand out in the robotics world by exploring the REPL and the event structure of Johnny-Five programs.

In the next chapter, we'll explore pins—including analog and PWM pins—and talk more about how an LED can be set to different values of brightness.