A mop is a cleaning tool typically constructed of absorbent materials at the end of a long pole. The absorbent materials are soaked in water or some combination of water and cleaning fluid and then dragged over dirty floors to clean up any dust, dirt, or debris.
First and foremost is your child's age and developmental stage. The older a child is, the longer he'll be able to play alone. For example, at 6 months, a child may be content by himself for 5 minutes; at 12 months, for 15 minutes; at 18 months, about 15 to 20 minutes; and at 2 years, for about half an hour.
But this is an argument coming from an adult who is playing a game that only has kids in mind. This is not a bad thing, to be certain, but it can be a real annoyance for the adult to play the game over and over again with kids. On the bright side, a single game will only take about 30 or less second. On the other hand, expect to play a lot of games in rapid succession. As mentioned above, the game does require counting, hand/eye coordination, and dexterity, but I think the child (and adult) are better served by going outside and kicking or throwing a ball.