Cero proposes a game against time. It is not a common clock that shows hours nor minutes, but it can still count time.
Cero consists of a main part and four little balls. Each of these balls represents an hour. After choosing how many balls  you wish to spend on a task,  place them on the top part of the body. One after another one, the balls will rotate inside the  main body and will come out of it after the hours has passed. Once inside, there is no chance to know where the balls are. Are you ready to make the best of Cero? Or are you going to loose your time?  One thing is sure, not being distracted by time will help you maximize it.