Save up the 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 do some things 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 loose the level.