Inside the cool laser-cut box is an Arduino Uno and a 9V battery, plus a current-limiting resistor and the all-important buzzer. ... to build a project based on your 1D LED pong, Arduino-style ...

The product page for that buzzer says "current consumption: 20 mA" These piezo buzzers can be corrected directly to a DC supply. There is no need for a current-limiting R (as for an LED).