For Japanese readers, I am happy to present a translation of my article on The Game, the Player, the World.
ゲーム, プレイヤ, ワールド : ゲームたらしめるものの核心を探る
This article is my take on the question of what a game is, whether there is anything in common between the things we call “games”, and why some games can be considered borderlines cases.
http://www.jesperjuul.net/text/gameplayerworld_jp/
A big thank you to Haruhisa Tanaka for the translation!