This undated rendering provided by Skyline Attractions shows Skywarp, a double-car roller coaster that features two cars speeding around each other on double loops. Skywarp will debut at Six Flags Discovery Kingdom in Vallejo, California, in the summer of 2018. It was one of a number of new attractions being talked about at this week's theme park expo in Orlando, sponsored by the International Association of Amusement Parks and Attractions. (Skyline Attractions via AP)