To help keep the game feel varied, and to test not only your platforming skills, but your gaming skills in all sorts of genres there are Mini-Levels set in different time periods. These allow you to earn extra stones in order to unlock further levels.
The first of which sees Clive as a fighter pilot working with the RAF (Rabbit Air Force) shooting down the evil LuftWoofer axis.
Technically speaking this introduces a whole host of new features such as a fully functioning radar in order to see the enemy planes, dual machine guns, volumetric clouds and more!