He It was developed by Alexey Pajitnov who was working for the Dorodnicyn Computing Centre of the Academy of Science of the USSR in Moscow. He wrote it originally on an Elektronika 60, which was a terminal computer developed in the Soviet Union,
The genius of the game is that it is so simple. There are just 7 different shapes that fall and which you must rotate so that they form complete lines. Simple and yet compelling.
And even though the game was designed and developed 30 years ago, it is, of course, perfect for smartphones!
I found out about the anniversary because (the fantastic) Ian Dempsey mentioned it on his morning radio programme. He indicated that he has spent many hours playing it.
So 30 years on the game is still ubiquitous. A search on my new Android phone tells me that there are more than 250 matching apps. A search on scratch.mit.edu says that there are about 1,990 results!
If you would like to play Tetris (to celebrate the anniversary) then here are 2 pretty good Scratch versions:
http://scratch.mit.edu/projects/2767355/
http://scratch.mit.edu/projects/2569483/
Here is a picture of the latter version:
