He put the project out on Hackaday.io and also has a video tutorial you can see below. There are five input pins to the chip which lets you connect one analog pin to any one of 32 analog pins.

Arduino effectively handles analog inputs without the need for extra equipment ... microcontrollers from different companies. One example is Teensy, created by electrical engineer Paul Stoffregen ...

There is a boring part of every computer introduction class that shows how a computer is made up of input, output ... you get access to an analog joystick, two buttons, and an accelerometer.