Ralph Baer never meant to start a multibillion-dollar industry. He was just trying to get an idea out of his head and into the real world.
That idea, which went on to become the Magnavox Odyssey, served as a launching pad for game-makers, though—and virtually every developer and publisher today points to it as the moment the industry was born. Today, that industry is mourning the passing of Baer, who died at his New Hampshire home Saturday night at the age of 92.
"Thank you for birthing the lovely medium that has done so much for me personally and professionally," wrote Cliff Bleszinski, creator of the "Gears of War" franchise, on Twitter.
Baer first had the idea for a gaming system centered around the home TV in 1951, but his bosses weren't interested and instructed him to work on a different project. Some 15 years later, the idea was still lodged in his brain, and as he waited at a bus terminal in New York City for a co-worker, he began writing down notes.
When Baer got home that evening, he typed those up, filling four pages. Five days later, he put together a schematic. And by Oct. 20, 1966, he had created a working prototype, called The Brown Box.
The system, a console that hooked up to any television set, was basic—and so was the game he had created along with it. (A player, controlling one dot on a screen, had to chase another randomly moving one.) But when he showed the system to his bosses at Sanders Associates, a military electronics firm, he got the go-ahead (and funding) to continue research and development.
Read MoreHottest videogames for the holidays
In 1972, Sanders partnered with Magnavox to bring that Brown Box to people's homes under the Odyssey name. Priced at $100, the system sold 100,000 units in its first year—and eventually went on to sell 330,000 units. (Baer always thought it could have sold more, but felt Magnavox had priced it too high and hurt sales by implying the system only worked on Magnavox TVs.)
The numbers were high enough to spark a revolution, though. The Odyssey paved the way for companies like Atari, Nintendo, Sony and Microsoft to all create gaming systems of their own—which racked up much more impressive numbers.
Today, the video game industry is one of the fastest-growing fields in the entertainment industry. It employs more than 146,000 people, according to the Entertainment Software Association, and Gartner predicts the market will top $111 billion by 2015.
For comparison's sake, the video game industry posted brick-and-mortar sales last year of $12.97 billion in the U.S., according to The NPD Group, while North American box-office receipts for film studios came in at just $10.9 billion.
Baer may have launched the modern video game industry, but he never considered himself an avid fan of it. While he enjoyed an occasional sports simulation and kept up with trends, he wasn't enamored with many action games, having expressed a preference for heartier fare than endless shooting (though, Baer also acknowledged that he was hardly the target demographic for those games—and, in fact, also invented a game that let players shoot at the screen with a light gun).
Baer's contributions to pop culture weren't limited to video games alone. He was also the inventor of the popular electronic memory game Simon, which is still sold today. And he kept inventing long after he retired, holding more than 150 patents on various products.
Read MoreThe game that aims to cure lazy eyes
"Had I listened to all those people ... who were telling me to stop the nonsense or making comments like 'are you still screwing around with that stuff?' we might not all be here today," Baer said in 2008, when receiving the Game Developers Choice Pioneer Award. "It's a privilege to be here. Thank you very much. I appreciate the honor, and I'm still cranking out stuff. Goodbye."
