I wrote a tetris clone using Processing.org. I used no game framework and simply graphic and tweening libraries. I did it in about 6 weeks during a vacation between contracts. It was the hardest thing I had ever done at the time. I wrote a lengthy post about how I constructed it.
The source code is available here but it is not reference code by any stretch.
Downloads relocated … will have them up again soon.
This game study has no associate with the Tetris LLC or it's properties. If the name constitutes a breach of copyright, please contact @squarism on twitter.