Paul says it's a prototype. In 2008 Paul was right. It has since been finished by the original programmer and available through AtariAge. The game itself is a great addition to the 5200 and shows that the 5200 was in fact an arcade platform. All 99 levels are here, sounds were taken directly from the arcade, and the controls work well. If you own a real 5200 then you owe it to yourself to pick up a copy of Tempest. It's really good!