[Haskell-cafe] Tetris

If you were going to implement Tetris in Haskell, how would you do it? (For that matter, has anybody already *done* it? It would probably make a nice example program...) I'm particularly interested to know 1. How exactly would you do the graphical components? (Presumably there's some deep trickery with Gtk2hs that can draw free-form stuff like this.) 2. How do you implement a program that is fundamentally about state mutation in a programming language which abhors state mutation?