Racketball is yet another Pong clone, written in Racket. It's an attempt at writing a game in pure functional style. Though the rendering and input logic is mostly imperative, the game update loop; entity behaviour, controls, "AI", scoring, etc are all pure functional.
There are no external dependencies beside Racket itself, so after cloning the git repo, just run:
$ racket main.rkt
Racketball is available under the MIT License.