These notes assume that you are familiar with the game of Tetris.  If not, we suggest that you first read the Wikipedia entry on Tetris and then play the game a bit.
 

These notes also assume that you are familiar with Python and Tkinter as we have used them in our 15-112 course.
 

Here is Tetris approximately as we will write it:
   applet:  tetris.html
   jar file:  tetris.jar
   zip file:  tetris.zip (which is just a zip file containing tetris.jar)
Actually, those are Java applets/programs, and we will write ours in Python, but this can give you a clear idea of our design.
As should be clear when you run it, this is a simplified version of Tetris, and many interesting features have been left for you to add as bonus (see step 8 for details).

And here is a picture of the game in action (note that there have been some minor changes since these pictures were made, so you may notice some small cosmetic differences between them and the code above, such as the color scheme and where the score is displayed):


 

Our design includes two main elements:  a board and a falling piece.  In the picture, the board contains all blue (empty) cells except in the bottom three rows, where it contains various other colors.  The falling piece is the red piece in the picture.  In our design, this is not part of the board, but is drawn over the board.
 

More specifically, the board is a 2-dimensional list of color names (strings like "red", "blue", "green").  Initially, the board is full of one color, the emptyColor ("blue" in our sample code).  As falling pieces are transferred onto the board, other colors are introduced.
 

The goal of the game is to fill rows entirely with non-empty colors.
 

The falling piece is a 2-dimensional list of booleans, indicating whether the given cell is or is not painted in this piece.  For example, here is the definition of an S piece:
  sPiece = [
    [ False, True, True ],
    [ True,  True, False ]
  ]
 

As noted, the falling piece is not part of the board, but drawn over the board.  It becomes part of the board when it can no longer fall and we place it on the board, which will not happen until several steps from now in our design process.
 

The game is graphical and event-based.  This is achieved by using Tkinter as we have in previous animations..
 

Important debugging hint: remember that you can use the built-in ctrl-commands of our event-based animation framework. Critically, these include ctrl-r to reset, ctrl-p to pause, ctrl-s to step while paused, and ctrl-g to go (un-pause). These can be invaluable when trying to debug animations.

Many more details are available on the following pages.