User summary: A Certain Scientific Roleplaying Game uses skills and a d10 roll-under process to resolve opposed actions. The game's emphasis is on the adaptation of the setting presented in the Japanese-language "light-novel" series A Certain Magical Index (とある魔術の禁書目録 インデックス Toaru Majutsu no Indekkusu). The rules were developed on a public forum by various interested users, and are considered open to revision (though they have been stable since 2010).