Analysis of information sources in references of the Wikipedia article "Asteroids (video game)" in English language version.
The game program only allows 26 asteroids on the screen at any one time. …
In 1980, the company introduced Asteroids to compete with the Space Invaders arcade game, which was produced by another company. Atari's version proved to be a popular alternative. By the end of the year, 70,000 of the units had been shipped.