Tetris was developed in the Soviet Union by Alexi Pajitnov as sort of a fun side project while at his work. The game was eventually released and ported to other computers and across multiple platforms. Tengen and Nintendo had a bit of a bidding war/battle with the USSR and some others on getting the rights to manufacture their own versions of tetris. Ultimatley Nintendo won out but Atari games Tengen label put out their own version - the version here. However, in 1989, Nintendo slapped Atari with a lawsuit over the ill-gotten plans for the Rabbit Chip, and this game also caused even more legal battles, which is why Tengen is not as common to find as regular plain jane, Nintendo-regulatory gray cartridges, and why you'll NEVER see a proper Nintendo release of THIS version of Tetris (but rather the version I linked to which I also have).

And for the most part, it's the same game as Nintendo's. You have selectable music, you fill in lines of blocks to clear them, and if you clear 4 at a time, you get a "tetris", but to me, this version always felt a little more "bootlegged", a little more "Janky" compared to Nintendo's very polished release. But what this has - that Nintendo does not have, is simultanious split-screen multiplayer support, which this DOES have.

Then I found out about the whole Tengen thing over time. I remembered the Tengen black cartridges in my youth, with most of my friends having things like "RBI Baseball" on those cartridges. I found it a little odd because it seemed almost all NES releases were on the gray cartridges matching the styling of the system, and here were these weird black/gold cartridges by this mysterious company, which at the time I had no idea was tied to Atari, but given they had Gauntlet, Pac-Man, and some other franchises that were licensed to Atari (which I should have known given my 2600 collecting at the time), was just another brand name owned by the then already sold to Hasbro company.