[pygame] Background ghosts

["Michael Phipps" <michael.phipps@xxxxxxxxxxx>]

I am finishing up my first pygame; everything has been fun and easy except this:

The game is a tetris-like game (with a twist). I have the falling piece as a sprite. The background is just a bitmap. The pieces that have already fallen, I blit into place. So I have something like (in pseudo code):

def drawBoard():
    blit background to display
    for piece in fallenPieces:
         blit piece to display
   display.flip()

while 1: # game loop
    moveSprite()
    if sprite.nextLocation == taken
        fallenPieces.Append(sprite.asPiece())
        sprite = None
        removeSolidRows() # This removes fallen pieces that have formed complete rows
        drawboard()

The problem that I have is that as the sprite is falling, I can see rows that have been removed. I have confirmed that drawBoard() is doing the right thing - when the sprite hits the bottom and the screen redraws, the ghosts disappear. They are only there when the sprite floats over them. It looks like the sprite is getting the data from the old version of the screen (i.e. before the last piece fell and rows were removed) to redraw the screen's dirty regions.

Help!

Michael