In 1996, the Tetris Company launched the Tetris Jr., a pocket key chain Tetris. It was about 2½"×2" in size and thus probably the smallest way to play Tetris. As a publicity stunt, they distributed this freeware program, which emulated the key chain game very closely, offering the same eight games.

The buttons below the game window have no function. They are just
there for realism (Fernando Lagos did a better job with his
Simon in this aspect). To get started, simply
right-click anywhere on the
window, and a menu will pop up. Choose help
for an introduction
or simply start the game with the space bar. To move the window, you
can click anywhere too.
The version for 16-bit Windows is essentially exactly the same, only the key chain and the rounded corners are missing, since transparency in windows is not possible under 3.1. The interface is the same, too; this is the only 16-bit Windows program I know that uses right-click and pop-up menus!