If you don't consider Tetris one of the greats of gaming, you only have to look at, say, one of the Switch's most popular titles for evidence of its powerful legacy. That said, if you're unaware of the background of the 1984 puzzle game, developed by Russian Alexey Pajitnov, don't feel too bad — there's a video from Gaming Historian that'll fix you right up.
He then had to reduce the number of shapes due to working with "outdated hardware", bringing the count down from 12 to seven.
Six days later, Pajitnov had a playable game.
It's crazy to think that prototype would grow to become one of the most well-known games ever made, one that's managed to persist through generations of consoles and platforms. Let's just be glad Pajitnov didn't stick with original name for it: Genetic Engineering. A hard sell, that.
The Story of Tetris [YouTube]