This CSS, shared between PictureGame and QuizGame, is also present in the respective extensions' CSS files

For PictureGame, see:
/extensions/PictureGame/picturegame/maingame.css

For QuizGame, see:
/extensions/QuizGame/questiongame.css

Change-Id: Ib235697d492a62c6509e40f72ff349b4125b67c0