Blockbox is an online game on the casual gaming site GamePoint. The game has many different options, including the typical classic, 40 lines, and Marathon/Expert modes that simulate games in the Tetris The GrandMaster Series. The game also features multiplayer modes, chat, replays, and high scores.
Classic - regular gameplay.
40 Lines - 40 lines in the fastest time.
You must get to Level 15 in Classic mode to unlock Marathon 3. The rest are unlocked after playing Marathon 3 and getting to Level 200 or better.
Marathon 3.5 - Similar to Marathon 3 (but with a gravity progresion closer to TGM2), but a 10 second timer is activated whenever a x99 level is reached, which stops when the next section is reached, and restarts with the next x99 level. An M rank is achieved if there is 5 seconds or more left at the end of 1500 levels. GM is awarded if 10 seconds are left (which would be achieved by not stopping at any x99's).