Curiously missing from the abstract is their definition of "idle games". In the paper they define it as a games that "require players to leave the game and ret

Curiously missing from the abstract is their definition of "idle games". In the paper they define it as a games that "require players to leave the game and return to it at a later, unspecified point, where the game progresses on its own during that time and opens up different options for further play upon return."