This is one of my all time favorite games. It and Shenzhen I/O do a wonderful job of capturing the essence of what makes programming fun and put them into a game.
My biggest surprise from playing EXAPUNKS is how futile it is to try and pre-optimize a solution. I had to remind myself time and again to solve the puzzle first, then try and try and optimize it.
While the games are fun on their own, I recommend playing them at the same time as a friend. Trash-talking about finding more optimal solutions really added to the overall fun of playing the games.