Save up energy at your house by turning the lights off, when the last people has left the room.
In this game, you will see a floor map with peoples in it. These people will turn on the lights and spend some time in the rooms, then leave.
The challenge is you should turn the lights off after the people, to save the energy. However be careful, because if you turn the lights off in a room, where there is someone, you will lose that level.