A classic stage illusion now in close-up
A black ball is placed inside an empty trunk and a red ball is placed on top of the trunk's lid. The curtain surrounding the trunk is lifted up and immediately dropped. Instantly the red and black balls exchange places. The black ball is removed from the lid and the lid is removed to show the red ball now inside the trunk.
A mini version of the classic stage illusion called the 'Substitution Trunk' as performed by Harry Houdini and many stage illusionists today.
A clever mechanical principle makes the trick happen automatically.