You live in a house，but what about a tree house？ In the USA，many homes have yards（院子） with trees. Families sometimes build a small house in a big tree. These houses aren’t for living in. Kids play in them. There is often a ladder（梯子）. Kids can climb up it and go into the tree house. It can be very simple or fancy（精致的）. But it must be safe（安全的）. Kids will put games in the tree house and play with friends.