Monopoly (game)
When building and selling houses and hotels, you must build evenly - in other words, you may not buy or sell a house from a street if this would make the street have two more houses or two fewer houses than another street in the same color group. For example, you have to build one house on each street in a color before you can build a second house on any street in that color, and you must have four houses on each street in a color in order to buy a hotel on any of the streets in that color.