My team created this application for the 48 hour Clojure Cup hackathon. It's targeted at hackers looking for a fun way to sharpen their skills. It provides an interactive REPL, code editor (Ace), practice problems, and a game status / chat window for testing the practice problems and collaborating with other players.

Please try it out and vote for us if you like it. Comments and feedback are also appreciated, especially about any particular features you would like to see added next.