Although most people will connect Tetris with Nintendo thanks to the iconic Game Boy and NES versions, its one-time rival Sega also has a long association with the Russian puzzler.
Sega created an arcade version of the game prior to the rights situation being sorted out (the events of which are dramatised in Apple's Tetris movie), as well as a Mega Drive port – the latter of which was manufactured but never sold as a direct result of the rights being illegally sub-licensed at the time.
Sega would return to the series for 1996's Tetris S on the Saturn (developed by Bullet Proof Software, the same company that did the world-famous Game Boy version) and 1999's Sega Tetris, which launched on both the NAOMI arcade system and the Dreamcast.
One of the selling points of the home version was the ability to play online with other people, a function which naturally vanished the moment Sega turned off the Dreamcast's multiplayer servers. However, thanks to the efforts of @Shuouma_DC, it's now possible to play this game over the web once more.
There's a handy guide here on how to get your Dreamcast connected to the web in 2024, and you can download the pre-patched version of Sega Tetris – and other games which have been modified to work with this new system – here.