Tetris for Intro/Intermediate Programmers (Fall 2017 update)

Tetris for Intro/Intermediate Programmers (Fall 2017 update)
Step 6: Dropping and Placing the fallingPiece on the Board

We are now ready to have the falling piece respond to time events by dropping one row on each call to timerFired.
To start, we can have our timerFired function call moveFallingPiece(data, +1, 0), just as we do in response to a down-arrow key press.
This is not a bad start, but when it gets to the bottom, it just sits there (until we hit a non-arrow key to artificially reset the falling piece).
Once again, when the fallingPiece gets to the bottom, it simply stops falling and sits there -- it does not get placed on the board. To remedy this, we first need to know that it happened! That requires a small change to some code we have written. We will change moveFallingPiece so that now it returns True if the move occurred, and False otherwise for any reason (the piece moved off the board, or the piece collided with something on the board). This requires only a small change to our code. Once we have done this, our timerFired can test the return value from moveFallingPiece to determine if the move failed. In that case, we will use top-down design and call a function (that we are about to write) to place the falling piece on the board, followed by a call to newFallingPiece, to start a new piece falling from the top.
Writing placeFallingPiece:
This function (which only takes data, and not canvas) is quite similar to drawFallingPiece, only rather than draw the cells, we load the corresponding positions on the board with the fallingPieceColor. In this way, the piece is placed on the board.
Once you get this working, our game springs to life. This works quite well! But now we see another problem: the game never ends. The pieces pile up to the top, but then they just keep pouring out. We should fix this!
When should the game end? When we place a falling piece and it is immediately illegal. We can test for this in our timerFired, right after we call newFallingPiece.
But what should we do when the game has ended? Here, we will simply create a new variable, data.isGameOver, and set it to True. Then we will change the appropriate draw function to test this variable and if it is True simply draw a suitable message. Finally, we will let the user start a new game at any time by hitting 'r' for 'restart', and calling the init function in response. Remember also to disable your step and key event functions when the game is over until the user restarts a new game (though, again, be sure your keyPressed continues to look for the 'r' key, even the the game is over, or else it will be impossible to restart!).
At this time we will remove our test code from prior steps, both the call to newFallingPiece in response to a non-arrow key press and the four corners in init.

At the end of this stage, your Tetris board should be able to do this:

David Kosbie
Carnegie Mellon University
koz@cmu.edu