Don't let yourself get hung up on doing anything fancy, it's just fun to do. Seriously, just implementing tetris in processing is a fun way to spend an hour, and a great way to remind yourself of why programming is fun. It doesn't involve anything crazy as far as algorithms, but is a fun challenge to do. It's definitely worth it to implement a version, it is just fun to do.

+1! And there are plenty of helpful tutorials around if you get a bit stuck!

I found this a while back: http://javilop.com/gamedev/tetris-tutorial-in-c-platform-ind... It’s Tetris in C++, so it should be easy to adapt it to a C like language (or other if you can follow the logic)