The original bouncy house was essentially an air pillow with a roof, but the hundreds of modern models include inflatable waterslides, basketball gyms, a game in which players attempt to knock each other over with a large inflatable wrecking ball, and characters licensed from multimedia franchises such as Frozen. Thousands of companies now rent inflatable castles in the United States. The market has also diversified to include lighter retail designs. By 2014, the industry was estimated to be worth $100 million.