Need to be quiet? A small switch on the side shuts off the vibrations. The 4×4 keypad really allowed [Turi] to cram in a bunch of features using both short and long press to do different things.

For example, you can write code to drive a virtual NeoPixel 16×16 matrix. There’s even example ... playground including Charlieplexed LEDs, a keypad, and an LCD. There are also challenges.