For Dead Keys, the player progresses through a sequence of levels, one after another. Upon reaching the end of one level, the next begins. As the player moves from level to level, their progress should be saved so that the most recent player can easily resume their progress from the highest attained level on their next play session. To achieve this, we need to use only the PlayerPrefs class for storing the highest attained level. Progress cannot be resumed within a level, that is, the player may resume play from the highest attained level, but always from the beginning of that level.