This is a Tetris variant with only two types of blocks, called "Binary Tetris".There is no rotation, but it the same basic idea.
Yes, there are a few things to note, like the fact that the 'game' is pretty limited, and some people says it takes a few more bytes in order to call the routines. It also seems they aren't counting the number of libraries required to operate it, but it's a nice implementation that makes you remember the good old programming days.
And, if you're bored, you can always participate at the 140byt.es website and go for a challenge.
You can check the game's demo and its source code at the websites below.
SOURCE CODE: http://jsbin.com/egiqul/49
NEWS SOURCE: Tetris in 140 bytes (via) i-Programmer
Our thanks to 'Gauss' for a neat news story!