Complex sentence: He then floats down into an acrylic glass box, previously examined by 2 audience members, and continues to float inside after the box is covered; an assistant walks over the top, and Copperfield walks upside down moving his feet under the assistant's feet.
Split into simpler sentences: He then floats down into an acrylic glass box which has previously been examined by two audience members, and continues to float inside after the box is covered. An assistant walks over the top of the box, and Copperfield walks upside down moving his feet under the assistant's feet.