Before Pong, Super Mario Brothers and whatever app you just got finished playing on your iPhone, there was Tennis for Two. It's known as the first-ever video game, created in a New York lab in 1958. Though its status as No. 1 is debated among people who care about that sort of thing, Tennis for Two is widely considered to be the precursor for all video games that followed.
In a few weeks, people in New York will be able to play Tennis for Two as it was originally designed, thanks to a refurbishment of the original components.
Here's what it looked like in its original state:
With all that pushing back and forth, it sort of resembles a Caroline Wozniacki match.
If you're interested in the particulars, read about it at techradar.com.