Quinn is a free, "falling blocks"-style arcade game with simple, solid gameplay and thoughtful multiplayer extras. Quinn doesn't tinker with the time-honored format for this popular type of game: four-block "tetromino" shapes fall down a vertical game board, and you have to move and rotate them into a neat stack along the bottom. Every time you complete a horizontal row of blocks, that row disappears and lowers the entire stack, giving you more room to maneuver the infinite supply of incoming, ever-faster-moving pieces.
Quinn does the basics well--the game runs smoothly, and you can customize the appearance of the shapes and the game board with tons of user-created designs on the Quinn site--but what makes it exceptional is the easy-to-use multiplayer features, including in-game chat and an online leaderboard. You can have two-player tournaments on the same computer or over a local network, and you can also play online through public servers listed on the Quinn site. For the truly motivated, Quinn even offers "unofficial," hidden preferences that you can activate through the Terminal. Overall, Quinn is an excellent value and one of the best options on the Mac for a game of this type.