Tetris Online (Japan)

Tetris Online is an official online Tetris game for Microsoft Windows 2000/XP.
 * No ARE, IRS, IHS is present.
 * T-Spin recognition is regular 3-corner T.
 * DAS is very slow and useless.
 * Key assignments cannot be changed.
 * Time Attack, Challenge, Marathon, VS COM, Multi mode is present.
 * Time Attack: Well known 40-lines time attack mode.
 * Challenge: 10-minutes score attack mode. Unlike to the Tetris Zone, game ends immediately if the level timer runs out.
 * Marathon: Standard Tetris mode. Game ends in level 15.
 * VS COM: Battle against AI-controlled player.
 * Multi: Battle against other players.

Official Site