"Resistive" touchscreens are the type you're most likely to use in a DIY microcontroller project. These consist of two screen layers coated with a resistive material and separated by a small gap. When touched, the layers make contact, creating a voltage divider circuit. The resulting voltage is easily measured and correlated to position. The top layer of the touchscreen is just a clear overlay, though; what really makes it work is the layer underneath. Approaches to implementing a screen range from putting a printed sheet behind a touchscreen for a static touch interface—actually a fairly simple method to pull off—to something as full-featured as an LCD smartphone display. Here are the three main options.