There is gravity, but Tetris pieces are dropped from very high, and have achieved terminal velocity by the time they reach your board.

I know we're firmly into joke territory at this point, but anyway, if that were true, then line pieces would fall faster when oriented vertically than horizontally.

Clearly the real answer is that Tetris is played in a weightless vacuum, and that pieces are shot at a constant speed from somewhere offscreen.

>Clearly the real answer is that Tetris is played in a weightless vacuum, and that pieces are shot at a constant speed from somewhere offscreen.

Obviously not, since the speed increases as the game progresses (of course the planet could have increased its mass in the meantime).

The speed the pieces are fired at is constant within each round, and then increases between rounds.

Obviously the tetrominoes are being fired by a variable speed railgun and the current is being increased with each round.

Right, but this is called 'gravity' in the game, so I think it's what ggp was talking about