It is a long-established “escape game” that has gained popularity due to its difficulty level and the perfection of its endings. It has been played more than 6 million times in total. The objective of the game is for players to find items, make full use of them, solve the riddle, and escape from a closed room. The basic controls are click-only (keyboard is used to input some passwords), and the game is suitable for players of all ages and genders. In addition to Japanese, the game is also available in Korean and English.