What was the first video game?

There is no single answer, because it depends on what you count as a video game. The oldest candidate is a 1947 "cathode-ray tube amusement device", in which a player steered a dot across a screen to hit targets drawn on paper. The most popular answer is Tennis for Two, built in 1958, because it was the earliest known computer game with moving visuals made purely for fun rather than for research or to show off a machine.

Tennis for Two has a lovely backstory. William Higinbotham, a physicist at Brookhaven National Laboratory in New York, who had earlier led the electronics division of the Manhattan Project, wanted something lively for the lab's annual open day. He designed a game in a few hours and built it with a technician in three weeks. It showed a tennis court from the side on an oscilloscope screen, and each player had an aluminium box with a button to hit the ball and a knob to aim. Hundreds of visitors queued to play; the high schoolers, he said, were the hardest to pull away.

Then it was taken apart and forgotten for about twenty years, until lawsuits over video game patents brought it back to light.

The story kept moving fast. In 1962 programmers at MIT made Spacewar!, a duel between two spaceships that spread to other computers. In 1971 came the first game you could buy a turn on, the arcade machine Computer Space, and in 1972 Pong, the first commercially successful video game, arrived alongside the first home console.