Brettrix is a tetris-like game with lots of options, and lots of scope to be silly! You choose how many bricks there are per piece... with up to 40 bricks per piece it's fun just watching the shapes to see what they look like. You can also decide how many pieces fit in the window, what you get score for, the speed of the game and whether it speeds up. You can configure your own sets of gameplay and scoring options and have a high score list for each one. You also have a lot of control over how the game looks, such as the colours, textures, size and even shape of the blocks.
Mac OS X 10.2
||Mac OS X (tested in 10.2, probably works in earlier versions)