You are now going to work your way through the first four projects. These projects all use LED lights in various ways. You will learn about controlling outputs from the Arduino as well as simple inputs such as button presses. On the hardware side, you will learn about LEDs, buttons, and resistors, including pull-up and pull-down resistors, which are important in ensuring that input devices are read correctly. Along the way, you will pick up the concepts of programming in the Arduino language. Let’s start with a “Hello World” project that makes your Arduino flash an external LED.