Google is celebrating the 100th birthday of computer-science pioneer Alan Turing with a minigame based on one of his “thinking” machines.

Turing, who was born June 23, 1912, designed what he called “a-machines” (the “a” is for “automatic”) in 1936 to demonstrate principles of artificial logic. A-machines served no practical purpose - you couldn’t use one to do your taxes, for example - but they did establish a base set of knowledge for future computers.

“Google’s homepage presents you with a box with a five-digit combination of ones and zeros, a “tape” with another set of numbers, and a switchboard with toggle switches and arrows. When you press the green “play” button, the machine will follow the instructions on each switch in order. Your goal is to manipulate the switches so that the program will change the numbers on the tape to match the ones in the box,” VentureBeat says.

“Each switch issues different commands. Some move the tape back and forth, some change the numbers, and some even change the order in which the machine “reads” the directions. Successfully matching the numbers fills in one letter in the Google logo and takes you to the next puzzle. You can complete the first few tasks through simple trial and error, but if you want to complete the “e” puzzle without hurting yourself, you might want to pay attention along the way to what the different instructions do.”