Force sensors are really cool. They take the amount of force applied to them and return a signal. There are two different ones that I have used, and they are functionally the same. There is the one by Phidgets, in which we can easily make use of the code that we wrote for the light sensor. We can just attach a force sensor, which can than interact with a servo. We don't even need to change any part of the code.

The other option is a force sensor that is connected directly to the circuit. You can use it if you want to avoid a solution such as Phidgets. These are generally less expensive (around $7 USD).

The sensor that I use looks like a circle with a rectangle coming out of it, as shown in the following image:

It is not a complicated component to add to your circuit. You can connect it to your breadboard and as long as you connect it to the GPIO pins, you can read the output from the sensor. There are only two pins. So, if you adapt a previous script, you can easily read the sensor.