Choose a number of cities by typing ‘3’, ‘5’, or ’10’. Then, enter the largest number of 50K+ population cities you chose in each 10-degree grid square. Only green squares contain answers. When you have 2 left to go in a square it will fill in faintly yellow, 1 left it will be orangish, and all done it turns red. A time bonus is given for completing a square (it is greater for higher levels).