http://h34nug3iwqjf2376fmmzdhgqivckzemcujmarlptfqeqtq7vya47yyad.onion/2007/02/21/gtetrinet-multiplayer-tetris-with-some-twists/index.html
Also, the servers offer different ‘channels’, which have slightly different game-modes. For example, the tetrinet.de server has a #maps channel, in which the players do not start with an empty field but with some blocks/extras already there. Also, there is a #pure channel, in which the player can play a more classical multiplayer Tetris, without any extras at all.